Contact Allergy in Atopic Patients: What We Suspected and What We Know

Contact allergy in children was previously considered to be uncommon. However, data from the last decades have shown an increase in its prevalence, which is thought to result from more frequent exposure to allergens at a younger age, new trends in body piercing, use of cosmetic and pharmaceutical products, and participation in sports and hobbies. Factors that may influence the onset of sensitization in children are atopic dermatitis, skin barrier defects, and intense or repetitive contact with allergens. Although there are many similarities between adult and children with contact allergy, the patch test results obtained in adults cannot always be applied to children. Moreover, the notion of an association between atopy and contact allergy in children has been challenged. Experimental studies have shown that individuals with atopic dermatitis (AD) have suppressed contact sensitivity due to their disease. Patch testing should be considered at early stages in patients with AD; it is indicated not only when contact allergy is suspected but also in cases of persistent eczema on specific localizations, such as on the hands and the feet, around the mouth, and also in the umbilical region. Patients with AD should be tested when multiple exacerbations occur, even when they are treated, or when the dermatitis is asymmetrical. The most frequent contact allergens in children are metals, fragrances, hair dyes, adhesive and rubber chemicals, preservatives, and topical pharmaceutical products. Toys and portable electronic devices are another potential source of hapten exposure in children. Positive reactions in atopic children must be interpreted carefully, as atopic skin is readily irritated; this is specially the case for metals. Patch testing in children is safe, but false-positive reactions can occur. In addition, an abbreviated baseline series, supplemented with allergens suggested by the child’s history, should be tested. The fundamental relationship between atopic disease and environmental chemical exposure in children is complex and occurs more tightly than previously supposed.