From the newborn, it is formed by undeveloped sebaceous glands, and the injury can disappear naturally.

Suiji hairstyle

It often appears after inflammation, which may be related to the damage of sweat ducts. Sunlight irradiation, second-degree burns, epidermolysis bullosa, delayed porphyria, lichen planus bullosa, herpetiform dermatitis, pemphigoid, pemphigoid and X-ray irradiation can all occur.