Atopic dermatitis is a chronic inflammatory skin disease associated with genes, the environment, defective skin barrier function, and allergy. The risk of developing atopic dermatitis is much higher in those whose family members are affected. It can be thought that atopic dermatitis is associated with genetic influence. However, there are many cases where the skin symptom or test result is not similar even in twins, because environmental and developmental factors must play a role too. A 19-year-old men came to our hospital to do allergic tests. They were twin who both had an atopic dermatitis. They underwent a skin prick test, specific immunoglobulin E(MAST) and a blood test including serum total immunoglobulin E(Ig E). In specific Ig E, the brothers showed identical results, showing positive responses to ticks, animal hair, and nuts such as walnuts. The skin prick test also showed very similar responses, positive reactions with cockroach, walnuts, mugwort, and ticks. And their total Ig E level was 591.6IU/mL and 528.4 IU/mL, respectively. Many studies showed that genetic factors play an important role in the development of this disease. Also, there have been many studies on twins. However, as far as we know there are no studies showing identical positive reactions to multiple allergens in skin prick tests, specific Ig E, and similar level in total Ig E. In that sense, our case report is interesting.