5 Possible Causes of a Swollen Breast — and When to See a Doctor

The causes of a swollen breast range from hormone fluctuations to more serious medical conditions. While it's best to see a doctor if you're concerned about a breast enlarged beyond its normal size, there are signs that can help you determine what the underlying issue might be.

By far the most common cause of swelling or enlargement of the breasts in women is due to hormonal changes, says Paige Johnson, MD, an ob-gyn at the University of Tennessee Medical Center. "Women vary in how much they may experience this monthly with their menses, but they'll also experience breast swelling at other times, such as during puberty or menopause when hormones may flux rapidly," she explains.

Women can also experience breast swelling with changes in weight, fluid retention, after trauma or when a breast cyst develops, she continues.

The best advice for swollen breasts — or any changes in this body part — is to "know your breasts," says Dr. Johnson. "Breast tissue changes with your cycle and it may feel larger and more cystic the week before your period, so a monthly inspection to feel the tissue will allow you to know what your breasts normally feel like," she explains. Any mass that's new, enlarging or tender for more than a month should be evaluated by a doctor.

Read more: 7 Things That Might Cause Your Breasts to Get Bigger

Here's more about when you might experience a swollen breasts and what might be causing it.

1. Puberty

Young girls may experience swollen breasts when puberty begins, since the first sign of this life change is the development of tender breast buds, according to the American Academy of Pediatrics.

Puberty occurs when a girl's body starts producing high levels of female hormones in anticipation of adulthood. The Palo Alto Medical Foundation states that girls usually develop breasts between the ages of 7 and 13 years old, although some girls may develop breasts earlier or later. When girls enter puberty, tissue forms behind their breasts, causing the flat area around the nipples to enlarge and giving the appearance of swollen or enlarged breasts.

2. Medications

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"Many women experience breast swelling and tenderness with the initiation of oral contraceptive pills, when undergoing fertility treatments or with hormone-replacement therapy," says Dr. Johnson.

Other medications can cause hormone changes indirectly, such as thyroid medications, corticosteroids and some psychiatric medications, she adds. Talk to your doctor or pharmacist about the side effects of any medications you're taking.

3. Impending Menstruation

Women can experience breast swelling and tenderness as a result of an impending menstrual period, according to the U.S. National Library of Medicine. A woman's breasts may swell shortly before each menstrual period, only to decrease in size immediately following menstruation. Women who get swollen breasts during this time report feeling breast fullness, heaviness and tenderness.

"Women who experience swelling and pain one to two weeks prior to their menses cyclically may want to consider trying non-steroidal anti-inflammatory drugs, vitamin E, decreasing salt intake and limiting caffeine to see if their symptoms improve," Dr. Johnson says.

Read more: 4 Foods to Avoid During Your Period

4. Breast Infection

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Women with a breast infection may experience swollen breasts, per the U.S. National Library of Medicine. Breast infections often occur when the common bacteria Staphylococcus aureus enters the body through a break or crack in the skin, usually on the nipple. Infected fatty breast tissue can push on a woman's milk ducts, causing her breasts to swell and triggering painful lumps in the infected area.

Women who breastfeed may also experience breast infections due to blocked milk ducts. This particular infection is called mastitis and it can cause the breast to swell and become enlarged, red, warm to the touch and tender, says Dr. Johnson. "Women also often experience fever, chills and may have muscle aches," she continues.

To ease the pain of mastitis, women should consult with their doctors for antibiotics and continue to pump, breastfeed or express milk. "Anti-inflammatories such as ibuprofen are helpful for the pain and they also help decrease the swelling of the ducts, which allows better emptying of the breast," Dr. Johnson notes.

5. Inflammatory Breast Cancer

Inflammatory breast cancer can cause swollen breasts in some women, though thankfully it's rather rare. The National Cancer Institute estimates that 1 to 5 percent of all breast cancer cases in the United States are attributed to inflammatory breast cancer, which is a very aggressive form of the disease. It occurs when cancer cells block the lymph vessels in the skin of the breast causing it to become swollen, red and inflamed.

Women with inflammatory breast cancer may notice that the skin on their breasts has a pink or reddish-purple color that consist of ridges or pits that resemble the skin of an orange. The pitted appearance of the skin occurs when the breasts swell as a result of fluid buildup within the breasts. A combination of breast heaviness, burning, aching, increase in breast size and tenderness can signal inflammatory breast cancer.

"A breast mass may cause the breast to feel or appear enlarged or swollen, but it is important for women to know that greater than 80 percent of masses felt in the breast are not due to cancer," says Dr. Johnson. The most common breast masses women feel are cysts or benign tumors such as fibroadenomas, she adds.

If you have any of the above symptoms or feel a lump of some kind in your breast, it's important to make an appointment with your doctor right away.