Topical Treatments Carry Risk in Atopic Dermatitis

Children with atopic dermatitis (AD) were reported to have a greater risk for developing contact dermatitis from some common ingredients of topical products than those with a history of contact dermatitis but no AD, in a recent comparison of patch testing responses in both groups.

Although those with AD were more likely to react to particular substances, the prevalence of contact sensitization from a large series of potential allergens was similar in both groups, according to the report by principle investigator Maritza Middelkamp-Hup, MD, PhD, Department of Dermatology, Academic Medical Centre, University of Amsterdam, the Netherlands, and colleagues.

The similar rates of skin reactions in the study groups counter a widely held assumption that patients with AD are less susceptible to the development of allergic contact dermatitis (ACD). An additional revelatory finding of the study was that some of the substances associated with contact sensitization in patients with AD were among the ingredients of some topical products marketed as "hypoallergenic" for use in children in the US.

"It is important to consider ACD in children, especially in children with recalcitrant atopic dermatitis that flares regularly or does not seem to respond to therapy," Middelkamp-Hup and colleagues indicated.

The investigators identified 1083 patients treated at 3 university hospitals (18 years or younger) who had been administered allergen patch tests because of suspected ACD in the period from 1996 to 2013.

They retrospectively assessed the patch test results in 1012 of the patients with ACD, comparing reactions in those with and without AD. All patients received patch tests in the European baseline series, and those at 2 of the 3 hospitals received a routine supplementary series and additional allergens suggested by medical history.

The proportion of children with AD who were reactive to at least 1 allergen test patch (48%) was comparable to that in the children without AD (47%). The investigators noted this discovery — children with AD are just as much at risk of developing ACD as those without AD – goes against an assumption that was based in experimental studies.

The evidence of an altered immune system in AD involving a Type 2 helper T cell bias was thought to promote an activated immune response and decrease the risk of contact sensitization.

"On the other hand, patients with atopic dermatitis have impaired skin barrier function, which may allow allergens to penetrate the skin more easily and thereby facilitate contact sensitization," Middelkamp-Hup and colleagues speculated.

Although the rate of reactions in children with AD was similar to that of the comparison group, those with AD reacted to different types of allergens. Among the most frequently sensitizing agents for those with AD were lanolin alcohols. The lanolin-allergic patients were 1.4 times more likely to have history of AD than allergic, but lanolin-negative patients.

Researchers showed that cocamidopropyl betaine, a substance also frequently implicated in those without AD, most frequently associated with reactions in children with AD.

Although the high rate of reaction to this substance in both groups may have reflected its irritant, as well as allergenic potential, the investigators warn that the substance is commonly used as a surfactant in a range of personal care products, including some that have been labeled as "hypoallergenic."

The study was posted online November 11, 2016, in Contact Dermatitis.