Photosensitive dermatitis generally occurs when a patient's skin becomes allergic to certain wavelengths of rays in sunlight, resulting in allergic dermatitis. This type of allergic dermatitis is photosensitive dermatitis. Most cases of this dermatitis are caused by an allergic reaction to a specific wavelength of ultraviolet rays.

After patients develop this allergy, there are usually inflammatory erythema on the skin of the exposed areas. Or there may be papules and papulovesicles on the basis of the erythema. In some patients, due to the relatively severe inflammatory reaction, there may also be a certain amount of inflammatory exudation, and even symptoms of peeling. In some patients, due to the repeated recurrence of this inflammation, it may lead to local inflammatory pigmentation, or a certain degree of skin hyperplasia, as well as symptoms such as large patches of scales.