Round erythema on the surface of the breast may be related to skin diseases such as tinea corporis, pityriasis rosea, eczema, etc. It may also be related to mammary hematoma, capillary dilatation, lack of trace elements and other factors. 1. Tinea corporis, which starts as red papules protruding from the surface of the skin, with or without small blisters, and then forms scaly red patches with clear borders. 2. pityriasis rosea, which may appear as a single rose-colored oval or round plaque with a scaly surface and raised edges. 3. Eczema, which may appear as erythematous patches of skin on which pinhead to grain-sized papules and papules appear. It is recommended to visit a dermatologist if you notice any of the above diseases. 4. Mammary hematoma, caused by subcutaneous capillary rupture will lead to breast hematoma and thus cause local erythema, through the breast color ultrasound examination can be clear the scope of hematoma, and then treatment. 5. Excessive milk during breastfeeding will enlarge the breast, resulting in thinning of the breast skin and dilation of subcutaneous capillaries will cause red patches on the surface of the breast skin. 6. Lack of micronutrients in the body will lead to the appearance of red patches on the breast. 7. In the middle and late stages of breast cancer, the tumor volume grows too fast and too big, which will lead to varicose veins in the superficial skin, and the redness of the breast will look like red patches. Those who have round red spots on the surface of the breast should also consider mastitis and other causes such as inflammation of the breast skin. It is recommended to go to a regular hospital in time to clarify the cause of the disease and carry out standardized treatment under the guidance of the doctor, so as to avoid the delay of the disease and bring adverse effects to the body.