Contact Allergy in Children With Atopic Dermatitis

A Systematic Review

A.B. Simonsen; J.D. Johansen; M. Deleuran; C.G. Mortz; M. Sommerlund

Disclosures

The British Journal of Dermatology. 2017;177(2):395-405. 

In This Article

Abstract and Introduction

Abstract

The importance of contact allergy in children with atopic dermatitis is frequently debated. Previously, patients with atopic dermatitis were believed to have a reduced ability to produce a type IV immunological response. However, this belief has been challenged and authors have highlighted the risk of underestimating and overlooking allergic contact dermatitis in children with atopic dermatitis. Several studies have been published aiming to shed light on this important question but results are contradictory. To provide an overview of the existing knowledge, we systematically reviewed studies that report frequencies of positive patch test reactions in children with atopic dermatitis. We identified 436 manuscripts of which 31 met the inclusion criteria. Although the literature is conflicting, it is evident that contact allergy is a common problem in children with atopic dermatitis.

Introduction

Atopic dermatitis (AD) is the most common inflammatory skin disease in childhood, affecting 15–30% of children.[1,2] Although the pathogenesis of AD is complex and multifactorial, the disease has a common phenotypic expression, characterized by dry and itchy skin with chronic or recurrent episodes of dermatitis at typical anatomical sites.[3] AD was traditionally considered an immune-mediated condition, driven primarily by T helper (Th)2 cells,[4] and individuals with AD were considered less likely to have allergic contact dermatitis (ACD) owing to suppressed Th1-mediated cellular immunity.[5,6] Lately, this hypothesis has been challenged, and it is currently a topic of debate as to whether AD is caused primarily by a dysfunctional innate and adaptive immune system and an imbalance between Th1 and Th2 cells, or a primary skin barrier defect with immunological changes secondary to this, promoted by the invasion of trigger factors such as allergens and microbes.[7]

ACD is a type IV delayed hypersensitivity reaction that typically develops after repeated or prolonged topical exposure to chemical allergens. Clinically, AD and ACD may be difficult to distinguish as they both present as dermatitis and may coexist.[8] The relationship between the two is complex and the prevalence of contact allergy among children with AD is unknown. Whether children with AD have an altered risk of contact allergy compared with children without AD remains controversial, and studies have been conflicting. Theoretically, the impaired skin barrier in AD facilitates the penetration of potential allergens.[7] Indeed, children with AD are exposed to topical agents and emollients from an early age,[9] and the prolonged use of these agents could increase the risk of contact sensitization to both ingredients and vehicles. Several authors have highlighted the risk of underestimating and overlooking ACD in patients with AD.[8,10–12] However, experimental studies have found reduced sensitization among patients with AD compared with controls.[13–15]

The question remains whether patch testing to a greater extent should be used as a screening tool in these children, in order to exclude hidden allergies possibly maintaining or aggravating their skin symptoms. This article aims to review and summarize the existing knowledge on contact allergy and ACD among children with AD.

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