Typically this is an infection or a skin symptom common to developing breasts, breastfeeding or eczema. However, if time, antibiotics or other treatments don’t improve the symptom, it could be a sign of Inflammatory Breast Cancer. This type of cancer blocks the flow of lymph in the breast, which causes swelling and redness, but without an obvious hard lump. This may also make the breast feel warm or hot or cause a burning sensation.
If antibiotics don't clear up the redness after taking them for one week, then it’s best to see a breast specialist for possibly getting a “skin punch biopsy.” This is where a piece of the breast skin and the tissue immediately underneath is sampled for testing.