Itchy skin in summer when the skin is hot, the possible clinical causes are eczema, cholinergic urticaria, sweating herpes and so on. 1. Eczema: related to a variety of internal and external factors, the onset of the disease is mostly seen in the idiosyncratic group after contact with allergens, such as pollen, dust mites, animal hair and so on. Clinical manifestations of eczema include itching, pimples, erythema and other symptoms in the affected area. Eczema may also be induced by hot weather and increased humidity. 2. Cholinergic urticaria: limited edema occurring in the skin mucosa, associated with exercise, alcohol, spicy food and passive fever and other factors. After sun exposure in summer, it can be manifested as tiny and extremely itchy tingling masses appearing in many places all over the body, which can also be accompanied by headache, tearing and other symptoms. 3. Sweat herpes: related to ultraviolet radiation, mental state, dermatophyte infection and other factors. In summer, the weather is hot, the local skin is exposed to ultraviolet radiation and thermal stimulation, may induce or aggravate herpes perspiration, the clinical manifestations of pustules, itching, redness and erythema, and so on. It is recommended that patients with the above symptoms go to the dermatology department of the hospital in time for examination to make a clear diagnosis, so as to carry out targeted treatment.