What causes mastitis?

Other bacteria, including Streptococcus species, can sometimes be involved. Not every episode starts with infection: swelling and inflammation related to milk congestion can occur first, and bacterial infection may develop in some cases.

During lactation, milk congestion, oversupply, missed feeds, nipple injury, or ineffective milk transfer can contribute to inflammation. Bacteria normally found on skin or in a baby's mouth may then reach breast tissue, particularly when the nipple is damaged. Mastitis can present with a tender, hot, swollen area of one breast and may be accompanied by fever, chills, aches, or fatigue.

Breast pain alone does not identify the organism or prove that antibiotics are needed. A clinician uses the symptom pattern, breast examination, feeding history, and response to supportive care to distinguish inflammatory mastitis from a bacterial infection or an abscess.

Continue breastfeeding or expressing milk at a comfortable, physiologic frequency unless your clinician gives a specific reason to stop. Avoid forceful deep massage and repeated extra pumping, which can worsen swelling or drive oversupply. A cool compress, rest, fluids, and a pain reliever that is suitable for you may ease discomfort.

Arrange clinical assessment if symptoms are marked, worsening, or not settling with supportive measures. Antibiotics are used when bacterial mastitis is suspected and should be chosen by a clinician based on allergies, local resistance patterns, and previous infections. A lactation consultation can help correct latch, pumping, or milk-transfer problems that keep inflammation going.

Seek urgent medical care for confusion, faintness, difficulty breathing, rapidly spreading redness, or feeling severely unwell. Contact a clinician promptly for fever with a painful red breast, pus or bloody drainage, a new soft or fluctuant swelling, or symptoms that worsen despite treatment. A persistent lump after inflammation settles also needs examination because an abscess or another breast condition may require imaging.

Ask whether the findings suggest inflammation, bacterial mastitis, or an abscess; whether breast imaging or a milk culture is appropriate; which pain medicines fit your health history; and how to feed or express without increasing swelling. Mention medication allergies, previous resistant infections, nipple damage, oversupply, and any recent antibiotic use.