What are the causes of pain under the left breast?

Updated November 21, 2016

Pain under your left breast can be caused by a condition called costochondritis. When the cartilage that is located between your ribs becomes inflamed, this results in costochondritis. The ribs generally become inflamed at the juncture where they attach to your sternum or breastbone. Your joints in this area can swell as a result of costochondritis.


According to the Loyola University Health System and, this condition can cause pain in your breasts.

Before Your Period

Right before your menstrual period, when there are higher prostaglandin levels in a woman’s body, these prostaglandins can escape into the bloodstream from the uterus and have an affect on your muscles, causing pain in your breasts.


You may feel pain in the front of your rib cage and a dull, aching pain in your chest as well as in your breasts. If you touch your ribs they are sensitive and sore.

Other Causes

Pain in the lower left breast can also be the result of irritation to your chest wall, irritation to the chest wall muscles, or due to pleurisy, which is inflammation of the lining called the pleura, located between the lungs and the chest wall.


Breast pain can indicate something other than costochondritis. Make an appointment with your physician and get an official diagnosis.

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About the Author

Cindi Pearce is a graduate of Ohio University, where she received her bachelor’s degree in journalism. She completed both the undergraduate and graduate courses offered by the Institute of Children’s Literature. Pearce has been writing professionally for over 30 years.