What Is Mastitis?

Medically Reviewed by Renee A. Alli, MD on July 10, 2023
3 min read

On a good day, your breasts can feel tender. They're always out on the front lines, taking the brunt of every afternoon jog and pouncing toddler. They don't get infected often, but when they do, it can hurt like no bad bra or PMS pain ever has.

The catchall name for an infection of the breast tissue is mastitis. If you're breastfeeding, it's called lactation or puerperal mastitis. If you're not, it's called periductal mastitis. Mastitis can make you feel like you have the flu, but it can be cured a lot quicker.

Mastitis is a common condition in women who breastfeed. As many as 1 in 10 breastfeeding women in the U.S. get it. It's caused by a backup of milk in the milk ducts. This happens when your baby isn't sucking or attaching properly, or favors one breast over the other. Mastitis can also happen if you don't feed or pump regularly. It is more common in the first three months of lactation.

Breastfeeding women aren't the only ones who get mastitis. If you're not breastfeeding, a cracked nipple or nipple piercing can cause the breast infection. Both allow bacteria to get into the milk ducts. This is especially common in women who smoke.

Just like any other infection, the tissue around the infected area becomes inflamed to keep it from spreading to other parts of the body. With mastitis, the infected milk duct causes the breast to swell. Your breast may look red and feel tender or warm.

Many women with mastitis feel like they have the flu, including achiness, chills, and a fever of 101 F or higher.

You may also have discharge from your nipple or feel a hard lump in your breast.

The symptoms of mastitis can come on very suddenly. You may feel like you're getting the flu before you feel any discomfort in your breast. When you feel that pain or see the telltale redness, call your doctor as soon as possible.

Your doctor can diagnose mastitis based on a physical exam. The fever and chills give it away, as does a red, wedge-shaped area on the breast that points toward the nipple.

There are two things to rule out: a breast abscess, which happens when mastitis isn't treated quickly, and inflammatory breast cancer, which is rare and shares the symptoms of redness and swelling.

Whether or not you're breastfeeding, antibiotics should have you feeling better in a day or two. Take them as directed.

If you are breastfeeding, continue drinking lots of water, wearing loose bras, and resting as much as you can. Your doctor may suggest ibuprofen, or something like it, to take care of the fever and pain.

It's important to keep breastfeeding and move that milk in and out of the ducts. Continue expressing milk if it is too painful to feed from the breast. 

Tight bras and clothing put pressure on your breasts. Keep things light and loose.

To keep milk from backing up, make sure your baby attaches correctly, and get all the milk out of each breast during every feeding. Or, make sure you are pumping to express the milk on a routine schedule. A lactation consultant can help if you need support.