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When atopic dermatitis is really contact dermatitis


 

EXPERT ANALYSIS AT THE 2017 AAAAI ANNUAL MEETING

 

ATLANTA – When patients present with atopic dermatitis that worsens, changes distribution, fails to improve, or immediately rebounds, think contact dermatitis, Luz Fonacier, MD, advised at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.

Clinical signs of contact dermatitis include lesions with an atypical distribution/pattern, such as head, eyelid, or cheilitis/perioral predominance, or lesions on the hand or foot. Also elevate your suspicion in patients with therapy-resistant hand eczema, adult- or childhood-onset atopic dermatitis without childhood eczema, as well as in cases of severe or widespread dermatitis prior to initiating a systemic immunosuppressant. The list of potential allergens to consider includes metal (especially nickel, cobalt, and potassium dichromate), fragrances such as formaldehyde and balsam of Peru, preservatives, as well as topical emollients, corticosteroids, antibiotics, and antiseptics.

Dr. Luz Fonacier, allergist, professor of medicine Doug Brunk/Frontline Medical News
Dr. Luz Fonacier
If you choose to perform patch testing, the hypothetical detection rate of the T.R.U.E. Test (TT), compared with the North American Contact Dermatitis Group Screening Series is 69.7%-75.1%. Antigens on the TT but not on the NACDG series include thimerosal, gold, and quinoline mix. The TT also has a higher false-positive rate to neomycin, thiuram mix, balsam of Peru, fragrance mix, cobalt, and lanolin.

Dr. Fonacier, professor of medicine at the State University of New York at Stony Brook and section head of allergy at Winthrop University Hospital, Mineola, N.Y., recommends loading acrylates, fragrances, and allergens in an aqueous vehicle immediately before application. She noted that delayed patch test readings are common to metals, topical antibiotics, and topical corticosteroids, and that positive reactions to gold are often not clinically relevant. “The patch test positivity of gold can be as high as 30% in adults and a little bit less in children, but results from two large studies show clinical relevance in only 10%-15% of cases,” she said. A trial of gold avoidance may be warranted in patients with suspected jewelry allergy, facial or eyelid dermatitis, or exposure through gold dental restorations.

She went on to share tips for reading skin patch tests. The first reading should be done after 48 hours, while the second should be done 3, 4, or 7 days after application. “The second reading helps distinguish irritant from allergic responses,” she said. “Thirty percent of negative tests at 48 hours may be positive on delayed readings.” Most true allergic reactions occur between 72 and 96 hours. Allergens that may peak early include thiuram mix, carba mix, and balsam of Peru. Those that disappear after 5 days include balsam of Peru, benzoic acid, disperse blue #124, fragrance mix, mercury, methyldibromo glutaronitrile, phenoxyethanol, and octyl gallate. Delayed patch test reactions after five days include metals (gold potassium dichromate, nickel, and cobalt), topical antibiotics (neomycin and bacitracin) as well as topic corticosteroids.

Resources she recommended to attendees include the American Contact Dermatitis Society and the Contact Dermatitis Institute. Health and safety information about household products can be found here.

Dr. Fonacier disclosed that she has received research and educational grants from Baxter and Genentech. She is also a consultant to Church and Dwight and Regeneron.
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