A lot of pimples on the arms may be caused by conditions such as acanthosis nigricans, folliculitis, perifollicular keratosis, eczema, etc., which need to be removed by medication and general treatment under the guidance of a doctor. 1. Lichen planus: its etiology is not clear, can be seen on the arm cluster distribution, follicle consistency of small pimples. It is recommended to take oral vitamin A, vitamin E, etc., and topical salicylic acid ointment or gel and other medications under the guidance of a doctor. 2. Folliculitis: mainly caused by bacterial infections such as Propionibacterium acnes, treatment can be oral minocycline under the guidance of a doctor, topical clindamycin gel and other treatments. 3. Keratosis pilaris: mainly occurs in the upper arm extension, considering the genetic factors caused by, can follow the doctor’s instructions for external application of retinoic acid ointment and other treatments. 4. Eczema: mainly caused by allergies, due to sunlight allergy or eating mutton, seafood and so on. It is recommended to apply Denadyl ointment under doctor’s guidance, and oral anti-allergy drugs such as cetirizine can also be taken. In addition, daily life need to pay attention to diet and lifestyle habits, eat less spicy and stimulating food, but also pay attention to rest, do not stay up late and so on. A lot of arm acne may also be caused by other diseases, it is recommended to consult a doctor in a timely manner to clarify the cause of the disease under the guidance of the doctor to treat the symptoms.