Study compares results of allergy patch tests between children and adults

Adults and children who are referred for patch testing of allergens appear equally likely to have allergic contact dermatitis, although they tend to react to different allergens, according to a report in the October issue of Archives of Dermatology, one of the JAMA/Archives journals. Skin reactions to allergens are common among children, according to background information in the article. They can occur both on areas of the skin that come in direct contact with an allergen (contact dermatitis) and on areas that aren't directly affected (atopic dermatitis). Children suspected of contact dermatitis are often referred for patch testing, in which skin is exposed to various allergens affixed to a plaster tape to identify which cause a reaction.

Kathryn A. Zug, M.D., of Dartmouth-Hitchcock Medical Center, Lebanon, N.H., and colleagues analyzed results from 391 children age 18 and younger who underwent patch testing between 2001 and 2004. They compared results of the pediatric population to a group of 9,670 adults (age 19 and older) who were tested during the same time period.

Children and adults tested positive for at least one allergen at approximately the same rate (51.2 percent for children vs. 54.1 percent for adults). "Our study showed significant differences between the frequency of individual positive reactions to allergen patch tests in children and adults; children were more likely to have reactions to nickel, cobalt, thimerosal and lanolin, whereas adults were more likely to have positive reactions to neomycin, fragrance mix, M. pereirae (balsam of Peru [an extract from the balsam tree used as an alternative therapy]) and quaternium 15," the authors write.

The common positive reactions in children are expected given probable exposure patterns among this population. Some children reacted to supplemental allergens not included in common patch test series (15 percent) or in commercially available tests (39 percent). Children with a positive reaction were more likely to have atopic dermatitis included as one of their final diagnoses than were adults (34 percent vs. 11.2 percent).

"Patch testing in children suspected of having allergic contact dermatitis is a valuable endeavor. Despite their limited back size, an expanded allergen series helps to identify important positive relevant allergens. Allergen concentration does not need modification for testing in children," the authors conclude. "The top 45 allergens with the most frequent positive and relevant reactions reported in this study should serve as a guide to patch testing in children suspected of having allergic contact dermatitis in North America. Including supplemental allergens to the patch test materials based on clinical suspicion is also useful in some patients."

Source: JAMA and Archives Journals