If you have a rash under your armpit that looks like a spur, consider it to be a common wart caused by human papillomavirus infection, which can be treated with liquid nitrogen freezing or carbon dioxide laser. If the surface of the lesion is smooth, it may also be a skin flap. The skin flap can be left untreated, but you need to avoid local humidity and sweating to avoid pain and discomfort due to infection. If you want to remove it, you can directly choose to give iontophoresis or CO2 laser treatment after local anesthetic because the skin flab has a tip. After treatment, avoid contact with water, local dampness and sweating to avoid infection. In the case of common warts, it is also necessary to avoid picking and scratching to avoid increasing the lesions by inoculating themselves to other areas.