A pimple on the arm is also very painful, considering the possibility of folliculitis, acne, etc., the treatment is mainly based on drug therapy. 1. Folliculitis: pay attention to the local skin clean and dry; oral antibiotic drugs, such as amoxicillin or cefadroxil; can also be used externally with ointment and ichthyol. 2. Acne: eat less high sugar, greasy food, pay attention to local cleanliness; can be used externally with erythromycin ointment, Vitamin A acid ointment, benzoyl peroxide and so on. If the above symptoms occur, the medication should be standardized under the guidance of a doctor.