Pain in the lower side of the right breast is usually considered to be related to breast hyperplasia, mastitis, pleurisy and other diseases. 1. Mammary hyperplasia: It may be due to the increase of estrogen, which proliferates the breast tissue and ductal system, and then causes the pain in the lower side of the right breast. Breast enlargement may also cause swelling and burning sensation. 2. Mastitis: Mastitis can be caused by inflammation of the mammary gland, which in turn causes pain in the lower right breast. Mastitis may also present with symptoms such as redness, swelling, breakouts, and chest tightness. 3. Pleurisy: It is usually due to the irritation of the pleural inflammatory mediators around the chest, resulting in pain on the right side of the lower side of the breast, pleurisy is usually accompanied by symptoms such as fatigue, chest tightness. In addition, breast trauma, breast fibroma, herpes zoster, breast cancer may also appear similar symptoms, in daily life, should keep the local skin clean, pay attention to rest, avoid overwork, appropriate exercise, improve the body’s immunity.