Underarm redness, swelling, pain, like broken, commonly due to the following reasons: First, skin infection, when the skin follicles appear infected, it can appear red, swollen, painful, while there is a break. At this time, you can locally rub iodophor or Bactrim and other drugs for anti-inflammatory, but also oral anti-inflammatory drugs commonly used, such as cephalosporin or penicillin. Secondly, it may be caused by the rupture of the growth swelling, such as sebaceous cyst infection. It is necessary to go to the general surgery department or emergency department of the hospital for examination. If it is these diseases, it is necessary to perform debridement to remove the infected necrotic tissues and then perform regular drug changes. Third, it may be caused by lymphatic inflammation. When lymphatic inflammation is more serious, there will be local redness, swelling, pain, and rupture with fluid flow. It is necessary to go to the hospital to improve the examination, such as blood routine, C-reactive protein, ultrasound, etc., and give related treatment.