Acne on chin and forehead is mainly considered to be related to folliculitis, acne, dermatitis, flat warts and other diseases. 1. Folliculitis: it can lead to red pimples on the affected area and gradually develop into papular pustules. 2. Acne: Commonly known as pimples, after the pores are clogged, bacterial infections may occur, leading to pustules and other symptoms. 3. Dermatitis: Diseases such as contact dermatitis and atopic dermatitis can lead to pimples and papules. 4. flat warts: mainly caused by infection with human papillomavirus, which can lead to the appearance of flat or hemispherical papules. The symptoms may also be related to other diseases. It is recommended that patients seek medical examination as soon as possible, symptomatic treatment.