Atopic dermatitis ,which is also called atopic eczema, can be acute, subacute or chronically relapsing .The main feature of atopic dermatitis is serious pruritus and it has a high impact on the quality of life. Thus,the study aim to find potential risk factors and the relation between IL-31(Interleukin 31) and atopic dermatitis by this research. The study is a case-control study. The source of cases is from department of dermatology in Kaohsiung Medical University Chung-Ho Memorial Hospital and Kaohsiung Municipal Hsiao-Kang Hospital. I got 83 adult atopic dermatitis patients and 40 urticaria patients. The source of controls is from the health examinations in Kaohsiung City. I got 333 residents. After Statistically analyzing, we find work environment has a high impact in atopic dermatitis patients. We can find their ORs are between 7 and 9. Secondly, we find the relation between smoking and adult atopic dermatitis. This is an important finding in this research. Smoking packs are directly proportional to OR(adjust gender, age, environment),and they have obvious dose-response relationship. We use pack years to analyse data, and the OR is 1.058. It represents the smoking has significant effect. However, the effect of long-term smoking may be greater. As for the pathogensis of smoking, it needs more researches to prove in the future.