This disease is a dermal inflammation with obvious effusing tendency caused by many internal and external factors,characterized by polymorpous and easy chronic skin rashes with easy recurrence and serious pruritus. The pathogenesis of this disease is mainly a delayed allergic reaction caused by complicated internal and external irritable factors.

The patients maybe possess a specific constitution controlled by genetic factors and the allergen may be foodstuffs, medications, intestinal parasites, bacteria, pollens, animal furs, or cold, heat and sunlight. The occurrence of the disease may also be related to indigestion, endocrine disturbance, mental factors and focal infection.