Mastitis is swelling and redness, called inflammation, of breast tissue. It sometimes involves an infection. Besides causing swelling and redness, mastitis causes breast pain and warmth. An infection also can cause fever and chills.

Mastitis most often affects people who are breastfeeding. This is called lactation mastitis. But mastitis can happen to people who aren’t breastfeeding.

Lactation mastitis can cause you to feel run down, making it hard to care for your baby. Sometimes mastitis causes people to wean their babies earlier than they meant to. But continuing to breastfeed is better for you and your baby. This is true even if you’re taking an antibiotic.

Symptoms of mastitis can appear suddenly. They may be in one or both breasts. Symptoms may include:

When to see a doctor

See your healthcare professional if you have breast symptoms that worry you.

Milk that is trapped in the breast is the main cause of mastitis. Other causes include:

Risk factors for mastitis include:

Mastitis that isn’t treated or that is due to a blocked duct can cause pus to build up in the breast. This is called an abscess. An abscess most often needs to be drained surgically.

To avoid this complication, talk with your healthcare professional as soon as you get symptoms of mastitis. You may need to take a course of antibiotics.

Before you start breastfeeding, think about meeting with a breastfeeding specialist, called a lactation consultant. This can help you avoid complications such as mastitis.

Lower your chances of getting mastitis by following these tips:

Your healthcare professional does a physical exam and asks about your symptoms and medical history. You might have a breast ultrasound. Your healthcare professional might take out, called aspirate, some of the fluid in your breast. A culture of this fluid can help find the best antibiotic for you.

A rare form of breast cancer, called inflammatory breast cancer, also can cause redness and swelling that might be confused with mastitis. Your healthcare professional may suggest a mammogram or an ultrasound or both.

If your symptoms don’t go away after you take a full course of antibiotics, you may need a biopsy to make sure you don’t have breast cancer. Be sure to follow up with your healthcare professional after you’ve taken all the antibiotics.

Mastitis treatment might involve:

It’s safe to keep breastfeeding if you have mastitis. Breastfeeding helps clear the infection. Weaning your baby suddenly might make your symptoms worse.

You might see a specialist in breastfeeding, called a lactation consultant, for help and support. Advice on the best way to breastfeed might include:

To help yourself feel better:

You may be sent to an obstetrician-gynecologist. For problems related to breastfeeding, you may be referred to a lactation consultant.

What you can do

Make a list of:

Questions to ask your doctor

Be sure to ask all the questions you have.

What to expect from your doctor

Your healthcare professional might ask you:

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