There are many reasons for nipple hardness, still, pain, specifically seen in the following analysis: 1, high libido, nipple in the sex-sensitive period, when coitus is stroked by the appearance of swelling, pain, hardness, is a normal physiological phenomenon, do not have to worry about it. 2, external stimuli, such as cool towels or sudden intimidation will appear on the body’s response to the removal of stimuli will disappear. 3, nipple allergy, when contact with the external allergens nipple allergy, manifested as nipple itching, pain and hardness, need to be treated with medication anti-allergy and keep away from the allergic substances. Allergy, manifested as nipple itching, pain and hardness, the need for drug anti-allergy treatment, and away from the allergic substances. 4, endocrine disorders, before menstruation or menstruation by the influence of increased estrogen, nipple pain, hardness, and after the end of the menstrual period will disappear. Breast hyperplasia patients also have nipple hardness and pain during menstruation, which need to be treated in serious cases.