If you rub your breasts hard enough it may cause deformation of the breasts, soft tissue contusion and even mastitis. 1. Breast deformation: Kneading the breasts may cause breast deformation, sagging, as well as the development of the left and right breasts are not synchronized, the size is not the same and so on. 2. Soft tissue contusion: the glandular tissue inside the breast is fragile, if you rub and squeeze, it is easy to damage it, and in serious cases, it may also cause the local capillary rupture bruises, and even infections. 3. Mastitis: When the soft tissue of the breast and nipple is bruised, if bacterial infection is triggered, it will lead to mastitis, and the patient will experience redness, swelling and pain in the breast, which may lead to aggravation of the condition if it is not treated in time. It is recommended that patients seek timely medical treatment under the guidance of a doctor.