Itchy breasts on one side and not on the other, consider skin eczema, allergy, infection, nipple inversion and other conditions. 1. Skin eczema, hot weather, underwear is not breathable or the texture is not good, may repeatedly stimulate the skin to form eczema, breast itching. 2. Allergy, breast skin contact with special items or wearing new underwear may cause skin allergy and itchiness. 3. Breast infection, if the secretion in the breast ducts is not discharged in time or the resistance is decreased, it may cause infection of the breast ducts, which may also cause itching and discomfort, aggravation of symptoms, redness, swelling and pain. 4. Nipple inversion, if the nipple of one breast is inverted, the secretions in the breast ducts can not be discharged, which may also cause the expansion of the breast ducts infections, the early manifestation of itching, and severe pain. Itching on one side of the breast may be caused by diseases, try to go to the hospital in time for examination and diagnosis.