SAN DIEGO – The ubiquitous acrylates take home the Contact Allergen of the Year title for 2012.
"We chose them because acrylates are everywhere in the environment," said Dr. Donald V. Belsito, who announced this year’s winner at the annual meeting of the American Contact Dermatitis Society.
Acrylates are plastic materials that are formed by the polymerization of monomers derived from acrylic or methacrylic acid. First used in Plexiglas, these compounds have a wide range of applications, including: paints, adhesives, dental composite resins, printing inks, and artificial nails. Acrylates also are used in a number of medical devices, including contact lenses, hearing aids, and bone cement for orthopedic endoprostheses.
While monomers are very strong irritants and allergens, fully polymerized acrylates are relatively inert. "Patch testing is tricky, and I think that’s something that we’re just finding out about the acrylates," said Dr. Belsito, a professor of clinical dermatology at Columbia University in New York. "They’re very volatile. The stability of the [patch test] allergens is a major issue, and they should be frozen or refrigerated."
In addition, the concentration necessary to reveal allergic sensitization is close to the irritancy threshold. These molecules also can induce active sensitization.
The North American Standard Series (Chemotechnique screening series) has been found to identify many cases of acrylate allergy caused by the inclusion of methyl methacrylate and ethyl acrylate in the series. However, clinicians should not rule out acrylate allergy even if the initial screening is negative. (Dermatitis 2011;22:98-101).
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The acrylates found in artificial nails have been named the contact allergen of 2012.
When patch tested, acrylate-allergic patients often display multiple positive tests. Previously, this was thought to be caused by cross-reaction. However, more recent analyses have shown that most acrylate-based industrial products contain many other acrylates as impurities – and thus are not included on the material safety data sheets.
"Many of the so-called cross reactions could in fact be concomitant reactions," noted Dr. Denis Sasseville in his article on acrylates, published in the January/February issue of Dermatitis (2012;23:6-16 [doi:10.1097/DER.obo13e31823d1b81]).
Methacrylates are tested at 2%, acrylates at 0.1%, and cyanoacrylates at 10%, according to Dr. Sasseville, who is a researcher in the division of dermatology at McGill University, Montreal. It is believed that patch testing with methyl methacrylate, 2-hydrorxymethyl methacrylate, ethyl acrylate, ethylene dimethacrylate, triethylene glycol diacrylate, and ethyl cyanoacrylate will identify most acrylate allergies.
The occupational exposure for dentists in particular is quite high; classic dental acrylics (including methyl acrylate) will cross through latex and vinyl gloves within minutes. Double gloving is suggested.
In one Finnish study of dental personnel, dentists and other dental personnel were most commonly exposed to 2-hydroxyethyl methacrylate, triethylene glycol dimethacrylate, and 3,3-bis[4-(2-hydroxy-3-methacryoxypropoxy) phenyl] propane (Contact Dermatitis 2007;57:324-30).
Both Dr. Belsito and Dr. Sasseville reported that they have no relevant disclosures.