A lot of small rashes on the face may be caused by seborrheic dermatitis, contact dermatitis, keratosis pilaris and other diseases. 1. Seborrheic dermatitis: the cause of this disease is not clear, may be related to heredity, Malassezia infection, dietary disorders, neurological dysfunction, sebum secretion, etc., occurring in the scalp, face, chest and back, etc., can be manifested as a lot of small rashes on the face. 2. Contact dermatitis: this disease is usually caused by skin contact with exogenous special substances, stimulating the skin and triggering an allergic reaction, such as cosmetics, facial cleanser, pollen, animal dander and so on. The skin is mostly confined to the contact area and can be seen as pinpoint-sized dense pimples, so a lot of small rashes on the face may be caused by contact dermatitis. 3. Keratosis pilaris: studies have shown that the disease has a genetic predisposition, may also be related to the lack of vitamin A, metabolic disorders, hypothyroidism and other reasons, the typical symptom is that the lesions are follicular papules, which can occur in the face, buttocks, etc., so the patient may have a lot of small rashes on the face of the situation. When you find a lot of small rashes on the face, you should go to the hospital to clarify the specific cause.