Allergic dermatitis is the skin diseases caused by allergen, is mainly refers to skin irritation, itching and peeling after exposure to certain allergens. At present, the sensitizing potential of chemicals is usually identified and characterized using animal test methods. Due to the increasing public and political concerns regarding the use of animals for the screening of new chemicals, using in vitro cell lines instead of animal models has become a trend. The human cell line activation test is mainly by detecting changes in cell surface markers and in the signal molecules after exposure to chemicals. The issue has been verified its feasibility by many laboratories in Europe, America and Japan. But at present the clinical value has not yet been approved. After some further optimization, new markers and methods are being developed and validated.