The face suddenly grows a lot of small rice bumps may be related to acne, sweat duct tumor, cornu rashes, flat warts and other reasons. 1. acne: such as hair follicles sebaceous gland duct hyperkeratosis will affect the hair follicle wall shedding epithelial cells and sebum normal discharge, and then form acne, manifested in the face of the sudden growth of a lot of small rice grain pimples. 2. Sweat duct tumor: a kind of adenoma differentiated from the ducts at the end of the sweat glands, commonly found on the eyelids, forehead and other parts of the skin color, yellowish pimples, single or multiple, dense but not fusion. 3. Corns: retention cysts originating from the epidermis or epithelium of the appendages, commonly found on the face, especially around the eyes, may appear as small pimples of grain size, not accompanied by pain and itching. 4. flat warts: related to human papilloma virus infection, mostly in the face, limbs and other parts of the face, can be a small grain of flat protruding skin pimples. It is advisable to go to the hospital in time to get a clear picture of the cause of the problem and to have a standardized treatment under the guidance of the doctor.