The nipple swelling and hardening may be normal or may be a disease, for example: 1, female nipples are sexually sensitive areas, stimulation of the nipple during sex will make the nipple swelling and hardening, which is a normal physiological phenomenon, do not worry. 2, menstrual and premenstrual syndrome. The actual fact is that you can find a lot of people who are not able to get a lot of money from the internet. For example, breast enlargement, mastitis and breast cancer, breast enlargement is related to physiological period, usually no treatment is needed, but serious cases need to take medication; mastitis, milk stagnation, will also appear swollen and hard nipples, timely squeeze out the remaining milk, anti-inflammatory treatment; breast cancer will appear nipple retraction, painful symptoms, active surgery to assist chemotherapy, keep a good mood.