Self-identification of skin diseases can be identified by the shape of the surface of the rash. For example, eczema can present with a polymorphic rash such as erythema, papules, scaling, vesicles, oozing, scratch marks, crusting, etc. For contact dermatitis, the rash is more clearly defined and there is a clear history of allergy from exposure to allergenic substances, and can present with a rash like erythema and papules, accompanied by significant itching. Herpes zoster caused by viral infection, which occurs mainly unilaterally, can appear as erythema, clusters of blisters, and piles of blisters along the nerve line, and is accompanied by significant pain.