Skin allergies caused by sunlight

Skin allergy caused by sunlight is the acute phototoxic reaction on the skin caused by the exposed parts of the skin caused by excessive exposure to the medium-wave ultraviolet rays in sunlight. The mechanism is that when the skin tissue is irradiated with light, an antigen substance is formed, which sensitizes the body and causes an allergic reaction. Due to the superficial action of medium-wave UV, it is only manifested in the epidermis of the skin. In addition, after intense sunlight, the epidermal keratinocytes of the skin will be necrotic soon, and the release of the medium will cause the dermal blood vessels to expand, thereby causing tissue edema. Subsequently, the melanocytes under the intense irradiation of sunlight accelerate the synthesis of melanin, thereby darkening the tanned skin. Therefore, sunburn is usually 4-6 hours after intense sunlight, and erythema at the border of the irradiated skin appears. In severe cases, edema may occur, and it peaks in 12-24 hours. It is accompanied by local burning or tingling, and some may have itching. More severe cases may cause systemic symptoms such as fever, headache, nausea, and vomiting. Polymorphic solar dermatitis is manifested in exposed areas, such as the face, neck, forearm extension, back of the hand, etc., with erythema of different shapes, pimples, wind masses or blisters. The most characteristic of this performance is that the sun is worsened and the light is reduced. The disease often develops after being exposed to strong sun for the first time in spring. The pouch now has rash on the face, neck, and forearms, with exposed areas such as erythema, pimples, wind masses, or blisters. Polymorphism means that the rash in different patients is often different, showing polymorphism, but for a certain patient, the rash form is usually single.