A lot of small red rashes on the face may be caused by allergies, seborrheic dermatitis and other reasons. 1. Allergy: when the face for the first time to use unused skin care products or cosmetics, etc., may produce an allergic reaction, manifested in the surface of the skin appeared red spots, pimples and other symptoms, accompanied by varying degrees of itching, tingling, red and swollen and other manifestations. 2. Seborrheic dermatitis: Seborrheic dermatitis occurs in the head, face, chest and back, and may be related to heredity, sebum metabolism and other factors, manifested as erythematous pimples on the surface of the skin, flaking and other symptoms, accompanied by varying degrees of itching. A lot of small red rashes on the face may also have other causes, it is recommended to go to the hospital in a timely manner to improve the examination, to clarify the cause of the disease to give targeted treatment.