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 are the causes of seasonal pale erythema? The following is a brief introduction to the causes of seasonal light erythema: Seasonal light erythema is caused by an IgE-mediated delayed contact allergy caused by exposure to pollen antigens dispersed in the air at that time, which is also known as IgE-mediated delayed-phase skin reaction. In a study of these patients in Nanjing, Zhao Jian et al. found that these patients could have increased total serum IgE levels and positive pollen antigen prick test and pollen patch test. There was a significant correlation between serum total IgE levels and specific IgE, skin prick test and positive pollen patch test. Seasonal facial dermatitis caused by cedar pollen, increased IRE level and positive pollen patch test were also reported by Katsumi Oyama and Richi Kotori in Japan. Pollen antigens are an important causative factor in this disease, and its pathogenesis may be an IgE antibody-mediated delayed skin allergy caused by exposure to airborne pollen antigens. In Chinese medicine, the disease is thought to be caused by internal heat in the lung and stomach, combined with wind-heat external sensation. Seasonal dermatitis is a skin disease that has a clear relationship with the climatic conditions of summer. It is prone to occur in high temperature and humid environment.