There are many causes of dense small rashes on the face, such as allergic diseases, acne, infectious diseases, keratosis pilaris, cornu rashes and so on. 1. Allergic diseases: These include contact dermatitis, insect bite dermatitis, drug rash, eczema and other diseases, which may cause dense small rashes on the face, accompanied by itching. 2. Acne: acne’s closed mouth pimples lesions can manifest as a small, dense rash on the face. 3. Infectious diseases: for example, measles, scarlet fever, rubella, etc., may be manifested as a dense small rash on the face; bacterial infections caused by fungal infections of folliculitis, may also lead to a dense small rash on the face. 4. Keratosis pilaris: and genetic factors, as well as vitamin A deficiency, endocrine related, may cause the appearance of the skin of the face chicken skin-like changes, can also lead to a dense small rash on the face. 5. Corns: small cysts belonging to the dermis, which may lead to a dense small rash on the face. There may be other reasons for the dense rash on the face, it is recommended to go to the hospital in time for examination and treatment as prescribed by the doctor.