It may be caused by physiological factors, such as changes in hormone levels and the comfort of clothes, or pathological factors, such as mastocytosis, nipple cracking, mastitis, etc. A, physiological factors: nipple vague pain appears during pregnancy, generally due to the elevated level of human chorionic hormone to stimulate the nipple, as a normal physiological response. In addition, the uncomfortable underwear can also lead to vague pain in the nipples. It is recommended that women pick the right underwear for themselves, while ensuring that the underwear material is skin-friendly and breathable, in order to take care of breast health. The vague pain may also be caused by sebaceous cysts, which should be treated with oral anti-inflammatory drugs as prescribed by the doctor.