Contact allergy in atopic individuals in relation to allergen-specific immunotherapy.

Type I sensitizations and atopic dermatitis (AD) often appear in the same patient. Beneficial effects of allergen-specific immunotherapy (ASIT) in patients with both AD and type I allergies have been reported. The predisposing role of AD to the development of type IV sensitization is discussed. Whether ASIT for type I allergy also influences type IV allergies is unknown. To compare the number of contact allergies between patients with and without AD, before and after one year's treatment with ASIT. A controlled, single-blind multicentre study of children/adults with allergic asthma and/or rhinoconjunctivitis, treated or untreated with ASIT, was performed. The history of AD was collected using questionnaires. The number of contact allergies was assessed by patch testing with a baseline series. 205 individuals completed the study; 133 treated with ASIT (exposed) and 72 before starting ASIT (unexposed). For participants with AD, significantly more contact allergies were found in the groups of all children (p = 0.002), all exposed children (p<0.001), and all exposed study persons (p = 0.013). Independent of AD, significantly more contact allergies were noted in the groups of all unexposed adults (p = 0.004) and all unexposed study persons (p = 0.004). The higher number of contact allergies in patients with AD indicates that AD may be a risk factor for type IV sensitization in those with allergic asthma and/or rhinoconjunctivitis. The lower number of contact allergies in patients exposed to ASIT suggests an immunomodulatory effect on type IV sensitization.