The right side of the breast pain is considered to be caused by the following conditions: First, it may be the right breast pain caused by breast enlargement, which can occur in a single breast, there will be a swelling in the breast, breast pain, abnormal fluid outflow from the nipple, etc., especially after exertion, premenstruation, emotional disorder will be more obvious pain. Secondly, it may be unilateral mastitis. For women who are developing and breastfeeding, it is mostly caused by milk stagnation due to milk not being discharged from the right side in time, and there will be redness, swelling, hard lumps and pain. Third, it may be unilateral breast cancer, especially in the advanced stage of breast cancer, the pain is more intense. Fourthly, it may be caused by injury to the right breast. It is best to go to the hospital for an imaging examination to distinguish what is causing it and then treat it accordingly.