Redness on the surface of the breast does not necessarily mean mastitis. Redness on the surface of the breast may also be related to contact dermatitis, allergies and other reasons. It is advisable to go to the hospital in time to get a clear picture of the cause of the disease and treat the cause. 1. Mastitis: Patients may experience localized symptoms such as breast pain, redness, swelling, and fever, as well as systemic symptoms such as chills and high fever. It is usually caused by milk stagnation, infection, milk duct obstruction, breast trauma and other reasons. 2. Contact dermatitis: mainly manifested as local skin erythema, edema, papules and other symptoms, may be conscious of itching, burning, swelling and pain and other symptoms. Generally due to contact with the skin irritation caused by the material. 3. Allergy: skin hives, erythema, bright red or pale white, skin-colored wind, etc. can appear. It is generally due to excessive immune response caused by contact with allergens. In addition, inflammatory breast cancer, nipple eczema-like breast cancer may also appear the phenomenon of redness on the surface of the breast, redness on the surface of the breast suggests that the patient can go to the hospital in time, to clarify the cause of the disease, and treat the cause.