Formaldehyde-releasers in cosmetics: relationship to formaldehyde contact allergy

Transcription

1 Contact Dermatitis 2010: 62: Printed in Singapore. All rights reserved 2010 John Wiley & Sons A/S CONTACT DERMATITIS Review Article Formaldehyde-releasers in cosmetics: relationship to formaldehyde contact allergy Part 2. Patch test relationship to formaldehyde contact allergy, experimental provocation tests, amount of formaldehyde released, and assessment of risk to consumers allergic to formaldehyde Anton de Groot 1, Ian R. White 2, Mari-Ann Flyvholm 3, Gerda Lensen 1 AND Pieter-Jan Coenraads 1 1 Department of Dermatology, University Medical Center Groningen, University of Groningen, The Netherlands, 2 Department of Cutaneous Allergy, St John s Institute of Dermatology, St. Thomas Hospital, London, UK, and 3 National Research Centre for the Working Environment, Copenhagen, Denmark This is the second part of an article on formaldehyde-releasers in cosmetics. The patch test relationship between the releasers in cosmetics to formaldehyde contact allergy is reviewed and it is assessed whether products preserved with formaldehyde-releasers may contain enough free formaldehyde to pose a threat to individuals with contact allergy to formaldehyde. There is a clear relationship between positive patch test reactions to formaldehyde-releasers and formaldehyde contact allergy: 15% of all reactions to 2-bromo-2-nitropropane-1,3-diol and 40 60% of the reactions to the other releasers are caused by a reaction to the formaldehyde in the test material. There is only fragmented data on the amount of free formaldehyde in cosmetics preserved with formaldehyde donors. However, all releasers (with the exception of 2-bromo-2-nitropropane-1,3-diol, for which adequate data are lacking) can, in the right circumstances of concentration and product composition, release >200 p.p.m. formaldehyde, which may result in allergic contact dermatitis. Whether this is actually the case in any particular product cannot be determined from the ingredient labelling. Therefore, we recommend advising patients allergic to formaldehyde to avoid leave-on cosmetics preserved with quaternium-15, diazolidinyl urea, DMDM hydantoin, or imidazolidinyl urea, acknowledging that many would tolerate some products. Key words: benzylhemiformal; 5-bromo-5-nitro-1,3-dioxane; 2-bromo-2-nitropropane-1,3-diol; cosmetics; diazolidinyl urea; DMDM hydantoin; formaldehyde; imidazolidinyl urea; preservative; quaternium-15; sodium hydroxymethylglycinate. John Wiley & Sons A/S, Accepted for publication 22 July 2009 In the first part of this article (1), key data on formaldehyde-releasers used in cosmetics (benzylhemiformal, 5-bromo-5-nitro-1,3-dioxane, 2-bromo- 2-nitropropane-1,3-diol, diazolidinyl urea, DMDM hydantoin, imidazolidinyl urea, quaternium-15 and sodium hydroxymethylglycinate) were presented, including applications, frequency of sensitization, relevance of patch test reactions, and their frequency of use in cosmetics. In this second part, the patch test relationship of these chemicals to formaldehyde are reviewed and assessed whether products preserved with formaldehyde-releasers may contain enough free formaldehyde to pose a threat to individuals who are contact allergic to formaldehyde.

2 Contact Dermatitis 2010: 62: FORMALDEHYDE-RELEASERS IN COSMETICS: PART 2 19 Relationship between Formaldehyde-Releasers and Contact Allergy to Formaldehyde When patients are tested with formaldehyde and one or more formaldehyde-releasers, concomitant positive reactions may be observed to formaldehyde and (one or more) donors. It is often assumed that this is due to cross-allergy to formaldehyde (more correctly termed pseudo-cross-allergy in our opinion), i.e. that the patch test reaction to the donor is caused by the formaldehyde present in the test material of the releaser. In favour of this assumption is that often more than one releaser reacts in formaldehyde-sensitive patients, even when the preservatives are not structurally related (cross-reactions unlikely). In a recent study, for example, among 219 patients allergic to formaldehyde and/or formaldehyde-releasers (quaternium-15, diazolidinyl urea, imidazolidinyl urea, 2-bromo-2-nitropropane-1,3-diol, DMDM hydantoin, and ethylene urea/melamine-formaldehyde resin), 76 (35%) were positive to only one of these compounds, 53 (24%) reacted to two, 27 (12%) reacted to three, 31 (14%) to four, 25 (11%) to five, and 7 (3%) patients reacted to six of the tested formaldehyde(releasing) materials (2). Of 59 patients, patch test positive to quaternium-15 1% petrolatum (pet.), 31 (53%) were also allergic to formaldehyde (tested 2% aqua). However, of seven patients allergic to quaternium AND to 2-bromo-2- nitropropane-1,3-diol, imidazolidinyl urea, or both, ALL were also allergic to formaldehyde, attesting to the role of formaldehyde in multiple reactions to releasers (3). In a USA study with 454 patients allergic to formaldehyde, 38 patients (8.4%) reacted to both formaldehyde and two releasers and 4 reacted to all three donors tested (2-bromo- 2-nitropropane-1,3-diol, imidazolidinyl urea, and quaternium-15). Of these patients reacting to two or three releasers (suggesting formaldehyde to be the cause), quaternium-15 (which probably releases the most formaldehyde) was positive in ALL (4). Perret and Happle investigated 13 patients with positive patch test reactions to diazolidinyl urea 2% aqua. Six of them were also allergic to formaldehyde. All 13 patients were additionally tested with the formaldehyde-releasers urea formaldehyde (8% aqua), glyoxal urea (10% aqua), and quaternium-15 (1% pet.). All six patients reacting to diazolidinyl urea AND to formaldehyde also reacted to the other releasers, whereas of those patients not allergic to formaldehyde, NONE had a positive reaction to any of the formaldehyde-releasers. It was concluded that in the six patients allergic to diazolidinyl and formaldehyde, the reactions to diazolidinyl urea were probably caused by formaldehyde in the patch test (5). Such studies, of which there are many, indicate that at least in a number of patients coreactions between formaldehyde and releasers are due to formaldehyde sensitivity. On the other hand, the investigation of Perret and Happle also indicates that sensitivity to diazolidinyl urea can exist independent of formaldehyde release, as none of the seven patients allergic to diazolidinyl urea but not to formaldehyde reacted to any of other releasers. The existence of allergy to the releaser 2- bromo-2-nitropropane-1,3-diol per se (independent of formaldehyde contact allergy) was demonstrated 25 years ago by Storrs and Bell (6). These investigators described seven patients reacting to patch tests with 2-bromo-2-nitropropane-1,3-diol 0.25% and/or 0.5% and/or 1% aqua or pet. They had all been sensitized by Eucerin cream, which was widely used in their geographic area as an emollient for dry and damaged skin, containing 0.05% 2- bromo-2-nitropropane-1,3-diol. The Eucerin cream was also patch test positive in all patients. None of them were allergic to formaldehyde and they did not react to either quaternium-15 or imidazolidinyl urea. All patients performing a ROAT for a maximum of 2 weeks on normal skin with Eucerin cream developed dermatitis. This indicated that 2-bromo- 2-nitropropane-1,3-diol allergy per se exists and that 0.05% 2-bromo-2-nitropropane-1,3-diol in a cream is sufficient to give a positive patch test and a positive ROAT in 2-bromo-2-nitropropane-1,3-diol allergic patients who are not sensitive to formaldehyde. In addition, the investigators had seen another four patients reacting to 2-bromo-2-nitropropane- 1,3-diol but NOT to Eucerin cream. These patients DID co-react to formaldehyde and to quaternium-15 and/or imidazolidinyl urea. They concluded that the amount of formaldehyde in the cream containing 0.05% 2-bromo-2-nitropropane-1,3-diol was insufficient to cause a positive patch test (6). How often are patients reacting to a releaser also allergic to formaldehyde? In many studies, patients have been patch tested with formaldehyde and one or more releasers, especially with quaternium-15, which is included in the baseline series in both Europe and the USA. This gives an opportunity to study the possible relationship between formaldehyde and the donors, at least in this diagnostic setting. In Table 1, data are presented on the frequency of co-reactions to formaldehyde in patients allergic to formaldehyde-releasers. There is a consistent picture for 2-bromo-2- nitropropane-1,3-diol. Less than 25% (and usually far less) of 2-bromo-2-nitropropane-1,3-diol-sensitive patients co-react to formaldehyde. This suggests that most patch test reactions to 2-bromo- 2-nitropropane-1,3-diol indicate sensitivity to this

3 20 DE GROOT ET AL. Contact Dermatitis 2010: 62: Table 1. Percentages positive to formaldehyde in patients reacting to formaldehyde-releasers a Country and period of study 2-Bromo-2-nitro-propane-1,3-diol Diazolidinyl urea DMDM hydantoin Imidazolidinyl urea Quaternium-15 Reference Number of patients % + formaldehyde Number of patients % + formaldehyde Number of patients % + formaldehyde Number of patients % + formaldehyde Number of patients % + formaldehyde Finland % (7) UK % 78 55% 64 53% % (8) USA b 69% b 515 b 83% b 756 b 63% b (9) Germany % (?) (10) IVDK % % 85 15% 64 47% (11) Austria % 36 11% 70 27% (12) UK % 91 25% % % (13) USA % (14) USA % 87 46% % (15) The Netherlands % (5) UK % (3) UK % (3) USA % (15) USA < % (16) a Only studies with at least 10 positive reactions to the releasers are included. Data on <10 patients are presented in Refs (2, 6, 7, 17 21). b Mean numbers/percentages in two patient groups reacting to the releaser in water and to the releaser in pet. vehicle.

4 Contact Dermatitis 2010: 62: FORMALDEHYDE-RELEASERS IN COSMETICS: PART 2 21 Table 2. Percentages positive to formaldehyde-releasers in patients allergic to formaldehyde a Country and period of study Number of patients allergic to formaldehyde Percentage of patients allergic to formaldehyde with positive reactions to: 2-Bromo-2- nitropropane- 1,3-diol (%) Diazolidinyl urea (%) DMDM hydantoin (%) Imidazolidinyl urea (%) Quaternium-15 (%) Reference Finland (7) UK (8) USA (9) UK (13) Austria (12) USA (4) USA < (16) a Only studies with at least 20 positive reactions to formaldehyde are included. Data on <20 patients are presented in Refs (2) and (6). Table 3. Testing with DMDM hydantoin and its parent compound in patients allergic to formaldehyde (22) Group I. 14 patients tested with DMDM hydantoin Concomitant allergy to DMDM hydantoin Patients allergic to formaldehyde 3.0% (only) 1% (also) 0.3% (also) Negative 1% only = % and 0.3% = % and 0.3% and 0.1% = Group II. 21 patients tested with MDM hydantoin Concomitant allergy to MDM hydantoin Patients allergic to formaldehyde 3.0% (only) 1% (also) 0.3% (also) Negative 1% only = % and 0.3% = % and 0.3% and 0.1% = preservative per se and are not related to formaldehyde allergy. The picture for quaternium-15 is also fairly consistent. In all but two studies, half the number of patients or more reacted to formaldehyde, indicating that formaldehyde is in >50% of the cases responsible for the quaternium-15 patch tests. Less consistent are the figures for diazolidinyl urea (12 81% formaldehyde co-reactions), DMDM hydantoin (37 83%), and imidazolidinyl urea (11 63% co-reactions to formaldehyde). How often are patients reacting to formaldehyde also allergic to one or more formaldehyde-releasers? The reverse situation, i.e. what percentage of patients allergic to formaldehyde reacts to the releasers, can also be deducted from many studies. The available data are shown in Table 2. For 2-bromo-2-nitropropane-1,3-diol, the data are consistent: less than 10% of patients allergic to formaldehyde react to 2-bromo-2-nitropropane-1,3- diol. On the other side of the spectrum, in all but two studies at least 30% of the patients reacting to formaldehyde also reacted to quaternium-15. Less patients (<30%) will react to diazolidinyl urea, and stillfewer (<23%) to imidazolidinyl urea. One study showed that about one out of five formaldehydesensitive individuals was also patch test positive to DMDM hydantoin. The relationship between positive patch tests to formaldehyde allergy and patch test reactions to DMDM hydantoin was investigated in detail by De Groot et al (22). Thirty-five patients allergic to formaldehyde were patch tested with formaldehyde and dimethylhydantoin (DM hydantoin; the parent compound). Twenty-one of these formaldehyde-sensitive subjects were also tested with MDM hydantoin (DM hydantoin +1 molecule formaldehyde), the other 14 also with DMDM hydantoin (two molecules formaldehyde). Test concentrations were % for formaldehyde, % for DMDM hydantoin and MDM hydantoin, and % for DM hydantoin, all in water (w/w). Control tests in 97 patients had excluded irritancy. The results are shown in Table 3. No patient reacted to the parent compound DM hydantoin. Of the 14 patients in Group I, 8 (57%) reacted to DMDM hydantoin. Of the 21 patients in Group II, 7 (33%) reacted to MDM hydantoin. In both groups, most negative reactions to (D)MDM hydantoin were observed in patients reacting only to the 1% solution of formaldehyde. Patients with stronger allergies to formaldehyde (reacting to 0.1% and/or 0.3% also) tended to show more positive reactions even to the lower concentrations of (D)MDM hydantoin.

5 22 DE GROOT ET AL. Contact Dermatitis 2010: 62: Table 4. Percentages positive to other formaldehyde-releasers in patients allergic to a particular formaldehyde-releaser Country and period of study Number of patients allergic to formaldehyde Percentage of patients allergic to releaser with positive reactions to: 2-Bromo-2- nitropropane- 1,3-diol (%) Diazolidinyl urea (%) Imidazolidinyl urea (%) Quaternium-15 (%) Reference 2-Bromo-2-nitropropane-1,3-diol UK (100) (8) UK (100) (13) USA (100) NT 5 14 (4) Diazolidinyl urea UK (100) (8) UK (100) (13) USA (100) (14) Imidazolidinyl urea UK (100) 47 (8) UK (100) 22 (13) USA NT (100) 40 (4) Quaternium-15 UK (100) (8) UK (100) (13) USA NT 17 (100) (4) NT, not tested. Using the data from Rosen and McFarland (23), it was estimated that 3% DMDM hydantoin contains 0.3% (3000 p.p.m.) and the 0.3% solution 0.02% (200 p.p.m.) free formaldehyde. Thus, 3 of 14 patients reacted to 200 p.p.m. upon patch testing. This may be comfounded somewhat by the fact that the patients were also concurrently tested with the higher concentrations and with formaldehyde (additive effect). These data demonstrate that aqueous preparations of DMDM hydantoin, in concentrations comparable to those used in cosmetic products, contain enough free formaldehyde to cause dermatitis in some patients allergic to formaldehyde when patch tested (22). How often are patients reacting to a formaldehyde donor also allergic to one or more other formaldehyde-releasers? In four large studies, the dynamics of patch test reactivity between the various formaldehyde-releasers was studied. The results are shown in Table 4. Again, for 2-bromo-2-nitropropane-1,3-diol, there is a consistent pattern: few reactions to and from other formaldehyde-releasers, formaldehyde plays a minor role. There is in two of three studies a very high co-reactivity between imidazolidinyl urea and diazolidinyl urea, higher than with formaldehyde, indicating (true) cross-allergy or a reaction to a common (non-formaldehyde) constituent (see under imidazolidinyl urea and under diazolidinyl urea, Ref. (1)). Of the patients reactive to diazolidinyl urea or imidazolidinyl urea, up to nearly half have reactions to quaternium-15, indicating a role for formaldehyde because these chemicals are structurally unrelated. Conversely, however, of the patients reacting to quaternium-15, only up to 23% react to imidazolidinyl urea and up to 30% to diazolidinyl urea. In such cases, the patient may well be allergic to formaldehyde, but the amount of formaldehyde in the diazolidinyl urea and imidazolidinyl urea test substances is not enough to cause a positive patch test reaction. The recent experience of the British Contact Dermatitis Society with formaldehyde and formaldehyde-releasers is shown in Table 5 (8). This table Table 5. Relationship between formaldehyde and formaldehyde-releasers: UK experience (8)) Formaldehyde (%) Quaternium-15 (%) 2-Bromo-2-nitropropane-1,3,diol (%) Imidazolidinyl urea (%) Diazolidinyl urea (%) Formaldehyde (100) Quaternium (100) Bromo-2-nitropropane (100) ,3-diol Imidazolidinyl urea (100) 75 Diazolidinyl urea (100) This table may be read as follows: horizontal row, 52% of patients allergic to formaldehyde are also allergic to quaternium-15 and 23% are also allergic to imidazolidinyl urea. Conversely, vertical row, 59% of patients allergic to quaternium-15 are allergic to formaldehyde, and 53% of the patients allergic to imidazolidinyl urea (55% for diazolidinyl urea) are also allergic to formaldehyde.

6 Contact Dermatitis 2010: 62: FORMALDEHYDE-RELEASERS IN COSMETICS: PART 2 23 may be read as follows: horizontal row, 52% of patients allergic to formaldehyde are also allergic to quaternium-15 and 23% are also allergic to imidazolidinyl urea. Conversely, vertical row, 59% of patients allergic to quaternium-15 are allergic to formaldehyde, and 53% of the patients allergic to imidazolidinyl urea (55% for diazolidinyl urea) are also allergic to formaldehyde. The associations between formaldehyde and the releasers were highly significant (Kendall s τ- b correlation score [P <0.001]); this was also the case for the associations between the various releasers (8). As the chemical structures of these compounds with the exception of diazolidinyl urea and imidazolidinyl urea are dissimilar, there is probably a major role for formaldehyde in these co-reactivities (which may then be called pseudo-cross-reactions to formaldehyde). Indeed, the strongest association is seen between formaldehyde and quaternium-15, known to release the most formaldehyde of the releasers. 2-Bromo-2- nitropropane-1,3-diol, on the other hand, releases little formaldehyde, and the association with formaldehyde, though statistically significant, is far weaker. Of course, concomitant ( dual ) sensitization to formaldehyde and the parent molecule may also contribute to these associations in a number of cases (11, 24). Experimental Provocation Tests with Cosmetics Containing Formaldehyde-Releasers in Formaldehyde-Sensitive Subjects Fifteen patients with contact allergy to formaldehyde (n = 7) and/or the formaldehyde-releasers quaternium-15 (n = 8), DMDM hydantoin (n = 1), imidazolidinyl urea (n = 2), and/or 2-bromo-2- nitropropane-1,3-diol (n = 6) but patch test negative to diazolidinyl urea underwent a ROAT (twice daily application to the antecubital fossa for 2 weeks) with a moisturizer preserved with 0.2% diazolidinyl urea. In only one patient, the ROAT was clearly positive. Afterwards, this patient was retested with diazolidinyl urea 1% pet. and 1% aqua and (now) had a positive reaction to 1% aqua but not to diazolidinyl urea 1% pet. The amount of free formaldehyde was not investigated. It was concluded that in patients allergic to formaldehyde and/or one or more formaldehyde-releasers, complete avoidance of other formaldehyde-releasers to which the patient is patch test negative is not always necessary, notably if the amount of formaldehyde released by that compound is below the threshold of reactivity for virtually all formaldehyde-sensitive individuals (around 250 p.p.m.) (2). It should be realized, however, that a ROAT on the neck or on the face may be positive in the absence of a positive reaction to the ROAT on the arm (25), so false-negative reactions may have occurred. Twelve patients allergic to formaldehyde performed a ROAT with a cream containing 1% DMDM hydantoin (twice daily for a week in the flexor aspect of the lower arm) and in four patients (33%), dermatitis was observed after 3 6 days. These four subsequently tested the same cream but now containing 0.25% of the preservative (estimated to contain approximately 200 p.p.m. free formaldehyde) in a ROAT; the test was negative in two, produced only itching but no visible changes in one, and provoked mild dermatitis in one (cave at: only 1 week) (22). It was concluded that cosmetics preserved with 0.25% DMDM hydantoin may pose a threat to certain patients allergic to formaldehyde. Zachariae et al. (25) performed an experimental use test exposure study with a cream preserved with diazolidinyl urea in patients allergic to formaldehyde. They developed a dose-escalating design, including four diazolidinyl urea concentrations, and exposure to three different anatomical regions (upper arm, neck, and face) each of 2-week duration. The test population consisted of 30 patients allergic to formaldehyde, 10 patients allergic to diazolidinyl urea (of which 7 had also reacted to formaldehyde) and 10 non-allergic controls. The four versions of the test cream were preserved with 0.05%, 0.15%, 0.30%, and 0.60% diazolidinyl urea (maximum allowed in the EU: 0.5%), which were found to contain 130, 370, 730 and 1500 p.p.m. formaldehyde, respectively. They were applied twice daily for 2 weeks on a 5 5cm area of the flexor aspect of the upper arm (ROAT). If no reaction occurred after 2 weeks, the cream application continued on the neck for another 2 weeks, and on the face, in a similar fashion, for further 2 weeks. If a positive reaction was observed at any time before the end of the 6-week period, the patient was examined and withdrawn from the study. The results were as follows: of the 10 formaldehyde allergic patients tested with the cream containing 0.05% diazolidinyl urea, none had a positive reaction. The cream preserved with 0.15% diazolidinyl urea elicited two reactions in 10 patients, 0.3% induced seven positive reactions and the ROAT with 0.6% resulted in seven positive reactions in 10 patients. Thus, with an increasing concentration of diazolidinyl urea from 0.15% to 0.6% (corresponding to formaldehyde concentrations of p.p.m., respectively), a dose dependent increase in patients reactivity was seen, not only in the number of reactors but also in the strength of the reaction. On the basis of this investigation, the amount of formaldehyde that does not elicit dermatitis in formaldehyde-sensitive subjects should be between 130 and 370 p.p.m.

7 24 DE GROOT ET AL. Contact Dermatitis 2010: 62: Of the 10 patients allergic to diazolidinyl urea (7 of which also reacted to formaldehyde), 9 had a positive ROAT to the cream with 0.15% diazolidinyl urea, 6 on the arm, and 3 in the neck (compared with 2 of 10 in patients reacting to formaldehyde but patch test negative to diazolidinyl urea) (25). There are several possible explanations for this: (i) Patients were not only allergic to formaldehyde but also to another compound in diazolidinyl urea (see also under chemical structure). The threshold for a patch test response is lowered by simultaneous presence of more than one allergen (25). (ii) These patients were more sensitive to formaldehyde (and thus reacted to formaldehyde and diazolidinyl urea) than those allergic to formaldehyde, for whom the amount of formaldehyde in the diazolidinyl urea test preparation was insufficient to elicit a positive reaction. (iii) In at least two patients with a positive ROAT, formaldehyde was negative. This may have been false negative. But if they were truly non-allergic, the allergy to the (other) compound in diazolidinyl urea that caused the reaction was strong enough to induce a positive ROAT. From these data, it may (tentatively) be concluded that levels of 370 p.p.m. formaldehyde ( %) released by a formaldehyde-releaser may under certain conditions of use induce allergic contact dermatitis on normal skin in a number of patients sensitive to formaldehyde. Some patients may react to even lower formaldehyde concentrations. When patients react to both formaldehyde and the releaser itself, the risk of developing allergic contact dermatitis increases. Isaksson et al. (26) have investigated whether the presence of 175 p.p.m. formaldehyde released from the preservative imidazolidinyl urea in a corticosteroid cream influences (i.e. diminishes) the cream s therapeutic efficiency in treating experimentally induced allergic contact dermatitis. In seven patients allergic to nickel and formaldehyde, patches of 8 9 cm of allergic contact dermatitis were provoked on the outer part of both upper arms. In a double-blind fashion, these were treated with a corticosteroid cream containing approximately 175 p.p.m. formaldehyde and (the other arm) with a corticosteroid cream of similar strength not containing formaldehyde. As controls served 17 patients allergic to nickel but not to formaldehyde. In two of seven patients allergic to formaldehyde (29%), the eczema treated with the formaldehyde-containing cream healed completely within 4 weeks, compared with 12 of 17 (71%) in the control group; the difference was statistically significant. There was no correlation between the formaldehyde reactivity, as measured by serial dilution testing, and the tendency to healing in the group allergic to formaldehyde and treated with the formaldehyde-containing corticosteroid cream. From this study, it may be concluded that the presence of 175 p.p.m. formaldehyde in a corticosteroid cream has a negative effect on the therapeutic efficacy of the corticosteroid on experimentally induced allergic contact dermatitis in patients allergic to formaldehyde and such creams should therefore not be used by formaldehyde allergic individuals (26). Flyvholm et al. (27) saw a positive reaction to a stay-on cosmetic preserved with 0.3% imidazolidinyl urea (containing approximately 300 p.p.m. free formaldehyde) in a ROAT lasting 1 week in one of three patients allergic to both formaldehyde and imidazolidinyl urea. In 20 patients with allergy to formaldehyde but negative reactions to imidazolidinyl urea, the ROAT produced some follicular papules in 5 of 20. These were considered to be a mild allergic reaction, as none of the controls subjects had any reaction at all (27). The Amount of Formaldehyde Released by Formaldehyde-Releasers There is only fragmented data available on the amounts of formaldehyde that will be released by formaldehyde donors. These amounts depend on the nature of the releaser, its concentration, the ph of the product, the temperature (the higher the temperature the more formaldehyde is present in solution after constant time) (28), the age of the product (upon storage increased levels of formaldehyde will be released), the level of microbial contamination, and the other constituents of the products containing the releaser (11, 28 30). The ph may greatly influence the release of formaldehyde. Diazolidinyl urea, for example, releases formaldehyde foremost in an alkaline product, i.e. with high ph value (31, 32). Imidazolidinyl urea in lower concentrations is stable in a low ph (acidic) environment, but with increasing ph the amount of free formaldehyde also increases (32, 33). The same holds true for DMDM hydantoin, whereas sodium hydroxymethylglycinate tends to release formaldehyde more in acidic solutions (32). In a 0.1% quaternium-15 solution, the amount of formaldehyde is strongly dependent on the ph: <200 p.p.m. formaldehyde at ph >9, p.p.m. at ph 7 and 600 p.p.m. at ph 3 (34). Other ingredients, i.e. the nature and composition of a product, may also influence the amount of free formaldehyde. In a protein-free shampoo, 0.1% quaternium-15 released 482 p.p.m. formaldehyde, but in a shampoo with protein only 122 p.p.m. Presumably, the protein forms complexes with released formaldehyde (23). In mascara preserved with 0.4% imidazolidinyl urea, the levels of formaldehyde were

8 Contact Dermatitis 2010: 62: FORMALDEHYDE-RELEASERS IN COSMETICS: PART 2 25 <10 p.p.m., but in creams or milks containing % the concentration of formaldehyde varied between 100 and 130 p.p.m. (28). Several methods for determining formaldehyde have been used (28, 32 38) which make comparisons difficult. None of the methods is absolutely reliable or does always give reproducible results, which may in part account for (sometimes greatly) varying results. With some methods (including the official EU adopted method), the releasers deliver in the presence of the reagent free formaldehyde continuously during its determination, which may result in too high and non-reproducible values (11, 28). Several tests are now available to overcome this problem (28, 32, 34, 36). It should be realized that free formaldehyde present in products preserved with a formaldehyde-releaser may not only originate from the releaser itself but may also comprise excess formaldehyde used to synthesize the preservative, formaldehyde from other formaldehyde-based raw materials used to prepare the cosmetic product, formaldehyde used as a preservative for the raw materials themselves, and from degradation of nonformaldehyde ingredients such as polyethyleneglycol ethers (39). Benzylhemiformal is the reaction product of benzyl alcohol and formaldehyde, and is rarely used in cosmetic products. It degrades rapidly in an aqueous solution, and at ph 5 the maximum possible amount of 300 p.p.m. formaldehyde of an 0.1% benzylhemiformal solution can be demonstrated (36). Emeis et al. (32) found that benzylhemiformal at 2% w/w aqueous solution mixes spontaneously, with decomposition of 97% of the benzylhemiformal. Higher dilution leads to instantaneous, complete decomposition of the releaser into formaldehyde and benzyl alcohol. At the maximum permissible concentration of 0.15% benzylhemiformal in cosmetic rinse-off products, the concentration of free formaldehyde should according to these authors be just under 0.05 wt% (500 p.p.m.) (32). 2-Bromo-2-nitropropane-1,3-diol only releases formaldehyde at higher ph values. Breakdown of 2- bromo-2-nitropropane-1,3-diol results in formation of formaldehyde and bromonitroethanol, a process which is accelerated by increased ph and/or temperature. The half life is more than 5 years at ph 4 but drops to 2 months at ph 8 (40, 41). Diazolidinyl urea is produced from 4 mol of formaldehyde and 1 mol of allantoin (compare: imidazolidinyl urea from 3 mol of formaldehyde and 2 mol of allantoin). From each molecule of diazolidinyl urea, four formaldehyde molecules can be released (4 mol formaldehyde/mole diazolidinyl urea). However, only about 50% of the theoretical amount of formaldehyde in diazolidinyl urea can be released upon complete hydrolysis (see diazolidinyl urea, chemical structure (1)). DMDM hydantoin is produced by reacting formaldehyde with DM hydantoin (5,5-dimethylhydantoin). The composition of DMDM hydantoin as determined by gas chromatography is as follows: 94 98% DMDM hydantoin, 2.5 3% MDM hydantoin (monomethyloldimethylhydantoin), other dimethylhydantoin formaldehyde products comprise the balance. One mole of DMDM hydantoin can release a total of 2 mol of formaldehyde. The concentrations of free formaldehyde depend on the ph; in alkaline environment more formaldehyde is released. DMDM hydantoin is said to contain 0.5 2% free formaldehyde and concentrations in cosmetics range from 0.1% to 0.6% (42, 43). It has been suggested that most formulations will, therefore, contain between 20 and 120 p.p.m. free formaldehyde (31, 44). However, these estimates may be too low, as a cream preserved with 0.15 wt% DMDM hydantoin contained wt% (130 p.p.m.) free formaldehyde (32). Imidazolidinyl urea is prepared from 3 mol of formaldehyde and 2 mol of allantoin (compare: diazolidinyl urea from 4 mol of formaldehyde and 1 mol of allantoin). From each molecule of imidazolidinyl urea, two formaldehyde molecules can be released (2 mol formaldehyde/mole imidazolidinyl urea) (44). Release is hastened by increased temperature and ph. Only about 75% of this theoretical amount of formaldehyde in imidazolidinyl urea will be released upon complete hydrolysis (44). Sodium hydroxymethylglycinate. Emeis et al. investigated the release of formaldehyde from sodium hydroxymethylglycinate with 13 C NMR spectroscopy (32). At a concentration of 1% and a ph of 5.5, sodium hydroxymethylglycinate decomposes completely into formaldehyde and sodium glycinate. In a basic environment, decomposition is incomplete. It is not until further dilution to 0.5% w/w the maximum concentration allowed in cosmetic products that it decomposes completely at a ph of 8.5. The concentration of free formaldehyde then is 0.12% w/w (1200 p.p.m.) (32). Rosen and McFarland (23) investigated protein and non-protein shampoos with the preservatives DMDM hydantoin, imidazolidinyl urea, diazolidinyl urea, and quaternium-15 added in concentrations of 0.1%, 0.2%, 0.4%, and 0.8%, and determined the amounts of free formaldehyde in the shampoos. In the first experiment, the shampoos were heated to steambath temperatures. It was found that DMDM hydantoin had released all its formaldehyde (2 mol/mole DMDM hydantoin) after 15 min, quaternium-15 had released its total of 6 mol/mole after 3 min and imidazolidinyl urea its 2 mol after 5 min. Diazolidinyl urea, theoretically able to

9 26 DE GROOT ET AL. Contact Dermatitis 2010: 62: Table 6. Formaldehyde recoveries from NON-PROTEIN shampoo containing various preservatives (23) Free formaldehyde Preservative DMDM hydantoin Imidazolidinyl urea Diazolidinyl urea Quaternium-15 Concentration (%) mg/kg (p.p.m.) % a mg/kg (p.p.m.) % a mg/kg (p.p.m.) % a mg/kg (p.p.m.) % a a Percentage of theoretical total releasable formaldehyde. release 4 mol/mole, released 2.1 mol after 5 min, and 3.3 mol/mole formaldehyde after 60 min at steam bath temperatures. In the second experiment, free formaldehyde was determined in the protein and non-protein shampoos at 23 C by a microdiffusion method. The results are shown in Tables 6 (non-protein shampoo) and 7 (protein-containing shampoo). As the concentration of each preservative is increased in the shampoo, the amount of free formaldehyde generated by hydrolysis increases. With increasing concentrations, the percentage of (theoretical) total formaldehyde released, however, decreases. The amount of free formaldehyde released changes when protein is incorporated into the shampoo, which is now depressed for all four preservatives when compared with the non-protein shampoos. This indicates that free formaldehyde has been complexed by the protein introduced. The order of formaldehyde release is imidazolidinyl urea <DMDM hydantoin <diazolidinyl urea <quaternium-15 (23). DMDM hydantoin and imidazolidinyl urea each contain two methylol groups while diazolidinyl urea has four. The molar percentages of free formaldehyde found for these three materials are about the same over the concentration range studied. An average of 1.3 mol of free formaldehyde per mole of preservative was found at 0.1%. This represents 65% of the formaldehyde in DMDM hydantoin and imidazolidinyl urea, but only 33% for diazolidinyl urea. This means that under the condition of the investigation only two of the four methylol groups are formaldehyde donors. The relationship of free molecular formaldehyde versus concentration for quaternium-15 is analogous to DMDM hydantoin and imidazolidinyl urea, even though quaternium-15 has six bound formaldehyde moieties. At 0.1% concentration, four of the six formaldehyde moieties are released, which is 66% of the total available (23). Karlberg et al. developed a method for quantification of formaldehyde in the presence of formaldehyde-releasers in skin-care products (45). They used this method to determine the amount of formaldehyde in cream and lotion preserved with formaldehyde-releasers by adding formaldehydereleasers in concentrations ranging from 200 to 2400 μg/g ( %) to diluted Essex cream and Essex lotion. Diazolidinyl urea and imidazolidinyl urea were added to the cream and 2-bromo-2- nitropropane-1,3-diol to the lotion. A linear correlation between the concentration of the formaldehyde donor and the amount of formaldehyde detected was found. The amounts (approximate, read from a graphic in the publication) results are shown in Table 8. Using quantitative 13 C NMR spectroscopy, the concentration of free formaldehyde was determined, released from diazolidinyl urea and imidazolidinyl urea compared with the maximum releasable concentrations of formaldehyde as a function of dilution and ph (Table 9) (32). In 8 of 161 rinse-off products and 124 leaveon products produced in various European countries and the USA, free formaldehyde levels of >0.05% (500 p.p.m.) were found with a maximum of 0.111% (1110 p.p.m.). Three of these products were labelled with quaternium-15 and one with diazolidinyl urea (46). In Switzerland, 19 of 34 Table 7. Formaldehyde recoveries from PROTEIN-CONTAINING shampoo containing various preservatives (23) Free formaldehyde Preservative DMDM hydantoin Imidazolidinyl urea Diazolidinyl urea Quaternium-15 Concentration (%) mg/kg (p.p.m.) % a mg/kg (p.p.m.) % a mg/kg (p.p.m.) % a mg/kg (p.p.m.) % a a Percentage of theoretical total releasable formaldehyde.

10 Contact Dermatitis 2010: 62: FORMALDEHYDE-RELEASERS IN COSMETICS: PART 2 27 Table 8. Amount of formaldehyde released with varying concentrations of formaldehyde-releasers (45) Formaldehyde-releaser Concentration of formaldehyde-releaser 0.02% 0.08% 0.16% 0.24% Free formaldehyde in the sample Diazolidinyl urea (in dil. cream) (p.p.m.) Imidazolidinyl urea (in dil. cream) (p.p.m.) Bromo-2-nitropropane-1,3-diol (in lotion) (p.p.m.) Table 9. Free formaldehyde released from diazolidinyl urea and imidazolidinyl urea as a function of dilution and ph (32) Diazolidinyl urea Imidazolidinyl urea 0.5% 0.2% (w%) 0.6% 0.2% (w%) Free formaldehyde (w%) ph (840 p.p.m.) (470 p.p.m.) (240 p.p.m.) (150 p.p.m.) ph (360 p.p.m.) (190 p.p.m.) (120 p.p.m.) (110 p.p.m.) ph (320 p.p.m.) (240 p.p.m.) (150 p.p.m.) (100 p.p.m.) Maximum releasable (w%) 0.21 (2100 p.p.m.) (860 p.p.m.) 0.14 (1400 p.p.m.) (460 p.p.m.) cosmetic products (56%) investigated for the presence of formaldehyde using three analytical methods including high-performance liquid chromatography were found to contain free formaldehyde in amounts ranging from 1 to 169 p.p.m.. Nine products contained more than 50 p.p.m.. In stay-on cosmetics, the highest concentration proved to be 145 p.p.m. (35). Other reports of free formaldehyde released from products containing formaldehyde-releasers are summarized in Table 10. The maximum levels permitted in the EU and the highest values of free formaldehyde found for these or lower concentrations are shown in Table 11. These data indicate that with the exception of 2-bromo-2-nitropropane-1,3-diol, for which adequate data are lacking in the right circumstances the amount of free formaldehyde released by all donors may be sufficient to induce dermatitis with regular use (48). Benzylhemiformal is permitted in rinse-off products only and may consequently pose less threat to formaldehyde-sensitive subjects. Discussion Relationship between formaldehyde and releasers and between various releasers There is ample evidence that patch test reactions to the various releasers in patients co-reacting to formaldehyde may be caused by formaldehyde in the patch test preparation. The mean percentages (adjusted for sample size) of patients allergic to a releaser that also react to formaldehyde in the various studies summarized in Table 1 were 15 for 2-bromo-2-nitropropane-1,3-diol, 49 for imidazolidinyl urea, 55 for quaternium-15, 57 for DMDM hydantoin, and 59 for diazolidinyl urea. It should be noted that in the cases of diazolidinyl urea, DMDM hydantoin, and imidazolidinyl urea, these percentages are heavily influenced by one major USA study with by far the largest numbers of allergic patients and high percentages co-reacting to formaldehyde (9). Nevertheless, these data do clearly show that, with the exception of 2-bromo-2- nitropropane-1,3-diol, about half the reactions or so (40 60%) to the releasers are caused by formaldehyde sensitivity. Of course, dual sensitization to formaldehyde and a releaser per se is also possible (11). Obviously, the fact that 85% of positive patch test reactions to 2-bromo-2-nitropropane-1,3-diol are seen in patients negative to formaldehyde, means not only that allergy to 2-bromo-2-nitropropane-1,3- diol per se (i.e. independent of formaldehyde) does exist, but that this is the case in the great majority for this releaser. For the others, about half of the cases are contact allergies independent of formaldehyde sensitivity. It should be appreciated that in a number of these cases, the reaction to formaldehyde may have been false negative, which would make the percentage reacting to formaldehyde in the test substance even greater. Conversely, not all patients allergic to formaldehyde react to one or more releasers, in fact it is a small minority (Table 2). The mean percentages (adjusted for sample size) of patients allergic to formaldehyde who also react to a releaser in the various studies summarized in Table 2 were 16 for 2- bromo-2-nitropropane-1,3-diol, 20 for diazolidinyl urea, 19 for DMDM hydantoin, 14 for imidazolidinyl urea, and 40 for quaternium-15. Whether or not a formaldehyde-sensitive individual will react to one or more releasers is dependent on the strength of the formaldehyde sensitization and on the amount of formaldehyde present in (aqueous test substances) or releasable by the test preparation (pet.). Thus,

11 28 DE GROOT ET AL. Contact Dermatitis 2010: 62: Table 10. Reports of free formaldehyde released from products containing formaldehyde-releasers Amount of free formaldehyde Formaldehyde-releaser Present in (type of product) Concentration (%) % p.p.m. Benzyl hemiformal Preservative solution (28) Shampoo (28) 2-Bromo-2-nitropropane-1,3-diol Shampoo (6) Emulsion (6) DMDM hydantoin Preservative solution 0.25 ph (32) ph (32) ph (32) Cream wt% 130 (32) Preservative buffer solution (33) Imidazolidinyl urea Shampoo (28) Milky cleanser (28) Cleansing cream (28) Mascara (28) Night cream (28) Preservative saline solution (47) Preservative buffer solution (33) Oil-in-water emulsion (27) Methenamine b Preservative solution 0.1 ph a (28) ph a (28) ph 8 10 a (28) Quaternium-15 Bath foam (34) Cleansing milk (34) Lotion (34) Shampoo (34) Sunscreen emulsion (34) product not specified (31) Shampoo (28) Eyeliner (28) Eye cream (28) Preservative solution 0.1 ph>9 <200 (34) ph (34) ph (34) Preservative buffer solution (33) Sodium hydroxymethylglycinate Preservative solution ph (wt) 0.12 wt% 1200 (32) Triazinetriethanol b Hand cleaner (28) a Approximate values, read from a graphic. b These releasers will be discussed in part 4. Reference one in about six formaldehyde allergic patients will also react to 2-bromo-2-nitropropane-1,3-diol and imidazolidinyl urea, one in five to DMDM hydantoin and diazolidinyl urea, and about two in five to quaternium-15, which indeed (Tables 6, 7, and 10) releases most formaldehyde of all donors. The relationship between strength of the reaction to formaldehyde and patch test reactions to donors was already clearly shown by de Groot et al., who demonstrated that patients with stronger sensitivities to formaldehyde (reacting to 0.1% and/or 0.3%) had positive DMDM hydantoin patch test reactions to test preparations with lower formaldehyde content (Table 3) (22). These findings are corroborated by the pattern of co-reactivity between the various releasers (Tables 4 and 5). 2-Bromo-2-nitropropane-1,3-diol patch test reactivity, for instance, is as mentioned above in only 15% attributable to formaldehyde. Indeed, co-reactivity to the other releasers was not even Table 11. Permitted EU use levels for formaldehyde-releasers and levels of free formaldehyde demonstrated at these levels Formaldehyde-releasers Permitted concentration (%) Product and concentration (%) Free formaldehyde (p.p.m.) Reference Benzylhemiformal 0.15 Preservative solution: (28) 2-Bromo-2-nitropropane-1,3-diol 0.1 Lotion: (45) Diazolidinyl urea 0.5 Non-protein shampoo: (23) Preservative solution: (32) Cosmetic cream: (25) DMDM hydantoin 0.6 Non-protein shampoo: (23) Preservative solution: (32) Imidazolidinyl urea 0.6 Oil-in-water emulsion: (27) Quaternium Non-protein shampoo: (23)

12 Contact Dermatitis 2010: 62: FORMALDEHYDE-RELEASERS IN COSMETICS: PART 2 29 in a single study in more than 14% of these patients. The highest percentages of co-reactivity were seen in quaternium-15, which is readily explained by the fact that this releaser has the highest formaldehyde content. In patients allergic to imidazolidinyl urea and diazolidinyl urea, many patients co-react to quaternium-15, for the same reason. However, the highest degree of coreactivity is between diazolidinyl urea and imidazolidinyl urea (up to 75% in several studies). This is not due to formaldehyde but to either crossreactivity or contact allergy to common ingredients in the test preparation such as compound HS [(4-hydroxymethyl-2,5-dioxo-imidazolidin-4-yl)- urea] or allantoin-formaldehyde condensation products (44, 49). Should cosmetics containing formaldehyde-releasers be avoided by patients allergic to formaldehyde and/or the releasers? When a patient reacts to formaldehyde and to, for example, diazolidinyl urea, it would be common sense to avoid cosmetic products containing diazolidinyl urea, at least the stay-on varieties. The same holds true for a patient reacting to the releaser itself but not to formaldehyde: avoidance is logical. But how to decide when a patient has a positive patch test to formaldehyde but not to any of the releasers or to one or two of the releasers (or when only formaldehyde and quaternium-15 are tested in the standard series)? Should the non-reactive releasers also be avoided (50) or may this be unnecessary (2)? Unfortunately, there are insufficient data to give firm and decisive recommendations, only tentative advice can be given. Whether or not a cosmetic product preserved with a releaser will elicitate an allergic reaction in patients sensitive to formaldehyde depends on: (i) the type of product; (ii) the mode of usage (frequency and location of application); (iii) the skin status; (iv) the strength of the hypersensitivity to formaldehyde; and (v) the amount of free and releasable formaldehyde in the product. Rinse-off products, in general, will have a low risk of causing allergic contact dermatitis. The daily use of stay-on products increases the risk (compared with products that are used infrequently or intermittently), especially when applied more than once per day, when used on sensitive skin such as the eyelids, the face, the neck, or the axillae, and when used on damaged skin, e.g. dry (dermatitis) skin in atopic individuals. It could be argued that, when there is a single reaction to formaldehyde but not to any of the releasers, the allergy to formaldehyde must be weak and poses little threat. However, formaldehyde being a difficult allergen with risk of both false-positive and false-negative reactions, such conclusions may not always be valid. Although we do not know what level of formaldehyde in products is safe, levels >200 p.p.m. probably are not (at least for some formaldehyde allergic subjects) (22, 48). The amount of formaldehyde in cosmetic products will depend on the releaser used for their preservation, its concentration, the age of the product, the ph, and other ingredients. Quaternium-15 releases the largest amounts of formaldehyde, followed by diazolidinyl urea, DMDM hydantoin, and imidazolidinyl urea. 2-Bromo-2-nitropropane-1,3-diol releases little formaldehyde (Tables 8 and 10). As Table 11 has shown, all releasers (with the exception of 2-bromo-2-nitropropane-1,3-diol, for which adequate data are lacking) can in the right circumstances of concentration and product composition release >200 p.p.m. formaldehyde, which may result in a number of patients in allergic contact dermatitis. Whether this is actually the case in any particular product cannot be decided on the basis of ingredient labelling. We thus recommend to advise patients allergic to formaldehyde to avoid stay-on cosmetics preserved with quaternium-15, diazolidinyl urea, DMDM hydantoin, or imidazolidinyl urea, especially when to be used regularly and/or on sensitive or damaged skin. When there is no alternative, products containing 2-bromo-2- nitropropane-1,3-diol may be tried. With products that the patient already possesses, provocation tests under normal usage conditions may demonstrate whether they are safe (or not) in this particular patient. The dose response phenomenon has sparsely been investigated with regard to formaldehyde and its releasers, and the clinical relevance of low values of formaldehyde in consumer products and cosmetics clearly needs further investigation. References 1. de Groot A C, White I R, Flyvholm M-A, Lensen G J, Coenraads P J. Formaldehyde-releasers in cosmetics: relationship to formaldehyde contact allergy. Part 1. Characterization, frequency and relevance of sensitization, and frequency of use in cosmetics. Contact Dermatitis 2010: 62: Herbert C, Rietschel R L. Formaldehyde and formaldehyde releasers: how much avoidance of cross-reacting agents is required? Contact Dermatitis 2004: 50: Ford G P, Beck M H. Reactions to quaternium 15, Bronopol and Germall 115 in a standard series. Contact Dermatitis 1986: 14: Fransway A F, Schmitz N A. The problem of preservation in the 1990s: II. Formaldehyde and formaldehyde-releasing biocides: incidences of cross-reactivity and the significance of the positive reponse to formaldehyde. Am J Contact Dermatitis 1991: 2: