Seasonal light erythematous patches, also called peach fungus, are called seasonal contact dermatitis in Western medicine. The disease occurs on the face of women and starts as flushed or light red coin-like patches with a few small red papules with indistinct borders and a small amount of scales attached. Itchiness or dryness is felt. It is sometimes accompanied by a history of allergic rhinitis or other allergic diseases. Because it tends to flare up in the spring and heals itself after the season, it is imaginatively called peach fungus in Chinese medicine. So, what conditions should be distinguished from seasonal pale erythema? The following is a brief introduction: Seasonal light erythema should be distinguished from seborrheic dermatitis, cosmetic dermatitis, and solar dermatitis. Seborrheic dermatitis also occurs on the head and face, with light red patches, mostly with greasy scales, and can develop in all seasons, without certain seasonality. Cosmetic dermatitis has a clear history of cosmetic application before the onset of the disease, and the rash site is consistent with the cosmetic application site with clear boundaries. Sunlight dermatitis is a skin disease caused by allergy to ultraviolet light, also has obvious seasonality, often occurring in the spring or early summer season, the rash is seen on the face, upper chest, forearms and back of the hands and other exposed areas, after sun exposure for 2 hours to 5 days in the light area, avoiding sunlight can reduce the rash, light excitation test or light patch test is of great value for diagnosis.