Common causes of milia on arms include folliculitis and perifollicular keratosis. 1. Folliculitis: this disease occurs mainly due to the inflammatory reaction of the hair follicle caused by bacteria, fungi and other infections. It manifests as reddish papules and pimples, which may be surrounded by a red halo. It can appear on the arms and looks like the symptom of having small rice pimples. 2. Keratosis Pilaris: Keratosis Pilaris is related to hereditary and other congenital factors, excessive high-fat diets can contribute to the production of inflammatory keratosis pilaris, and even concurrent infections appear folliculitis. It is recommended that patients go to the regular hospital dermatology consultation, follow the doctor’s instructions to clarify the diagnosis, active treatment, to avoid delaying the condition.