A pimple in the armpit is considered to be folliculitis, filiform warts, infectious molluscum contagiosum and so on. 1. Folliculitis: the armpit area has more hair follicles and is prone to sweating, if the hair follicles are clogged or irritated follicles cause an inflammatory reaction, folliculitis will appear, mainly red pimples, part of the folliculitis in the pimples on top of a white pustule. 2. Filiform warts: when the skin is broken, HPV virus will enter the epidermal cells through the broken place, and replication, proliferation of warts, mainly manifested in wart-like cumbersome organisms elevated in the skin, most of them are single, the tip of the papilloma. 3. Molluscum contagiosum: This is a skin disease caused by molluscum contagiosum virus infection, will appear in the trunk, armpits, elbow pit, thigh root and other inner folds, can be a separate one, or dozens or even hundreds of appearances, the surface of the pimple has a waxy glossy hard semiglobular papules, the center of the depression, usually no self-conscious symptoms. A pimple under the armpit may also have other causes, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, give targeted treatment or standardized treatment.