The main causes of skin in the mouth are the following: first, suffering from oral mucosal ulcers, work pressure, often stay up late, love to eat spicy, stimulating food, nutritional imbalance, vitamin and trace element deficiencies, it is easy to grow ulcers in the mouth, the typical symptoms of ulcers are mucosal congestion, redness, erosion and the appearance of white pseudomembrane. Secondly, mucosal diseases such as lichen planus and pemphigus are closely related to immune dysfunction. Lichen planus causes a white reticulation of the mucous membrane, and in severe cases, ulceration and erosion, while pemphigus is a more serious skin and mucous membrane disease, with the main symptoms being mucous membrane peeling, blistering and erosion. Third, the presence of Candida albicans or fungal infections in the mouth can also cause white pseudomembranes and peeling in the mouth. These two fungal infections occur mostly in people with low immunity and weakness.