Atopic dermatitis (AD) is a common skin disorder that is typified by itchy, inflamed skin. Although atopy is a prominent feature of AD, the cause of the disease is unknown, and approximately 10% of patients with AD are not atopic. The disease is under strong genetic control, so identification of the genes and genetic variants underlying AD might lead to new treatments and better classification of children with the disease. Preliminary genetic studies have identified that the genes or clusters of genes that affect the barrier functions of the skin are as important as genes that might modify the atopic process. These genes might influence other diseases, including psoriasis. The findings emphasize that the barrier function of the skin is not merely passive, and the polymorphic nature of genes and gene families expressed in the skin suggest a polyvalent response to a number of different stimuli, including infections.