Psoriasis is a recurrent, chronic skin disease with characteristic scaly erythema, which can become a dermatological disease for the following reasons: 1. 2, the polymorphic nature of the lesions, erythema, scaling, mossiness, etc., lesion form up to a dozen. 3, the diversity of damage, there are skin damage, damage to the digestive tract, damage to the motor system. 4. Easy recurrence, alternating remission and seizure, etc. 5.Irrational application of drugs.