Itchy nipples with residual milk after weaning may be caused by nipple allergy, mastitis, dermatitis and breast cancer. 1. Nipple allergy: Itchy nipples after weaning may be caused by contact with shoddy body lotion, wearing low-quality underwear or eating allergic foods. 2. Mastitis: The itchy nipples after weaning may be due to milk stagnation that is not cleaned up, which can lead to the formation of mastitis after secondary infection, resulting in itchy nipples accompanied by swelling and pain. 3. Dermatitis: If the surface of the nipple is dirty and not cleaned in time or if the immune system is poor, it is easy to cause dermatitis or eczema, which will lead to the symptom of itchy nipples after weaning. 4. Breast cancer: most breast cancer patients do not have clinical manifestations in the early stage, a small number of patients may appear nipple itching, pain, skin cellulite and other symptoms, so breast cancer may also appear after weaning with residual nipple itching symptoms. Patients with itchy nipples after weaning, should go to the hospital in a timely manner, to clarify the cause of the disease under the guidance of the doctor reasonable treatment.