1.What is photosensitivity dermatitis? It is an allergic skin disease caused by ultraviolet rays, which usually develops 1 to 2 days after sun exposure, with rashes on the face, neck and “V” shaped area in front of the neck, back of the hands and extensor side of the upper limbs, manifesting as small papules and small blisters, and self itching. 2.What is the general classification of photosensitive dermatitis? (1) Solar urticaria: It is a skin disease that occurs when the skin is exposed to the sunlight and it is itchy. It is often accompanied by headache, fatigue, nausea and other symptoms when it develops over a large area. (2) Chemical sun rash: It is an erythema, swelling, burning and itching that occurs after the skin has been exposed to the sun for a certain period of time. This reaction is distinguished from general sun rash by the fact that the lesions occur after the patient has taken or applied certain medications or cosmetics that increase the skin’s sensitivity to UV light. (3) Polymorphic sun rash: It is a common skin disease that occurs on exposed areas, such as the face, neck, anterior cervical triangle, back of both hands and both upper limbs, etc. Red papules, blisters and erythema with itching may appear. Most of the attacks or relapses are aggravated after sun exposure. 3.What are the factors that often cause photosensitivity dermatitis? Drug-induced photosensitivity dermatitis is often clinically misdiagnosed as general dermatitis and should be taken seriously. The main basis for diagnosing this disease is that the patient has a clear history of drug use before the onset of the disease, and the lesions are mainly distributed in light-exposed areas. The commonly used antihypertensive drugs such as Zhenju antihypertensive tablets and compound antihypertensive tablets contain thiazide diuretics, which have been reported in the literature to cause photosensitivity dermatitis. Some substances in life may increase the body’s absorption of ultraviolet light, should try to avoid exposure. For example, coal tar contains 25 known phototoxic substances; some poor quality perfumes, lipsticks and other cosmetics are also an important substance in photosensitive dermatitis. Some sunscreen products also have the potential to cause photosensitive dermatitis and should be chosen carefully. 4.How is photosensitive dermatitis treated? The actual dermatologist should guide you in your medication. Do not scratch the affected area, do not hot water to wash. 5.How to prevent the occurrence of photosensitive dermatitis? Summer is a high season for photosensitive dermatitis, people should do a good job of protection when engaging in outdoor activities, such as applying sunscreen, wearing sun hats, wearing long clothes and pants, playing umbrellas, etc.. Avoid eating a lot of vegetables that can cause photosensitivity such as black fungus, cilantro, celery, rape, spinach, cabbage, etc. When photosensitive skin disease occurs, you should go to the dermatologist in time.