If you’re experiencing pain in one or both armpits, the cause could be one of several conditions, ranging from skin irritation caused by shaving to lymphedema or breast cancer. Keep reading to learn more about the possible causes and treatments for your pain.

Following are some common causes for armpit pain.

Muscle strain

There are several muscles of the chest and arms that could cause armpit pain from overuse or injury.

The pectoralis major is a large chest muscle that runs up into the shoulder. It can be injured playing sports or lifting weights.

The coracobrachialis is a muscle in the upper arm that can also become strained from throwing sports, such as baseball, or from other activities, including tennis.

If any of these or other muscles of the chest or upper arm is sprained or becomes inflamed, you could feel the pain in the armpit.

Skin conditions

Shaving or waxing under your arms can irritate your skin. Certain deodorants or laundry detergents can trigger an allergic reaction. That can cause a rash called contact dermatitis.

These skin conditions are usually minor and temporary problems. Rashes, bumps, and other skin concerns may also be the result of more serious health problems. For example, hidradenitis suppurativa looks like acne under your arms, but is really a much more serious problem that can cause scarring. Fluid can also be released if the breakouts rupture.

Shingles

Shingles is another skin-related condition that can cause armpit pain. Shingles is an infection spread by the varicella-zoster virus. Shingles causes a scaly, uncomfortable rash that usually appears on your back, chest, or under your arms. Shingles can also cause a burning or tingling sensation.

Swollen lymph nodes

Your lymphatic system is a network of nodes or glands found throughout the body. Lymph is a fluid that helps fight infections. There is a concentration of lymph nodes near the armpit on both sides of the body.

Your lymph nodes may become swollen and tender if you have a cold or the flu. There are also several types of lymphatic conditions that can cause armpit pain. Lymphedema, for example, occurs when there is blockage in a lymph node and the fluid inside builds up. This swelling can be very painful. Lymphedema may follow breast cancer treatment or the removal of some lymph nodes that may have become cancerous.

Another condition, lymphadenopathy, also causes the lymph nodes to enlarge. It’s caused by an infection of the lymphatic system called lymphadenitis.

Breast cancer

Breast cancer is often painless in its early stages, but if you notice pain or feel a lump under your arm or in your breast, you should seek medical attention. The cause of the discomfort may be a benign growth, but it should still be evaluated.

Peripheral artery disease (PAD)

PAD is a narrowing of the smaller arteries in the arms and legs. That causes less oxygenated blood to reach the muscles and tissue of your limbs. Oxygen-starved muscles hurt. If you have PAD in one or both arms, you might feel that pain in your armpit.

Depending on the cause of your armpit pain, your symptoms may vary considerably. Skin conditions, such as inflamed hair follicles or shingles, will cause obvious rashes or other visible symptoms. Lymph node disorders, however, may be accompanied by swelling in the arm or armpit. You may also experience pain or swelling in the abdomen or legs if other lymph nodes are affected. Signs of breast cancer can include changes in the shape and size of the breast. Dimpling of the breast skin, known as peau d’orange, and changes to the appearance of the nipple may also occur.

If you believe your armpit pain is related to muscle strain, you may be able to fully recover by resting your muscles for a few days. If you have other symptoms, such as swelling or the presence of a lump, you should see your primary care physician. You may be referred to a hematologist who specializes in lymph node disorders or a breast cancer specialist if cancer is suspected.

If you see a rash or other signs of skin problems under your arm, then see a dermatologist.

If you suspect a lymph node disorder, and you have symptoms such as fever or congestion, you may have a respiratory infection related to your lymph nodes.

In most cases, early treatment of any condition will lead to better outcomes. If the pain is a temporary muscle-related problem, getting a diagnosis can also ease some anxiety, too.

If you have armpit pain that lasts for more than a few days or there are other symptoms, such as swelling or a rash, see a doctor right away.

Your doctor will exam your armpit and ask about other symptoms you have. They will also want to know when the armpit pain started. They may also examine your throat, ears, and skin to help with the diagnosis.

If they suspect a lymph node disorder or breast cancer, you may need a blood test and possibly a biopsy of tissue from a lymph node or, if present, a lump. The blood test may include a complete blood count (CBC) and a test for markers specific to the suspected condition.

Treating a strained muscle usually involves ice and rest for the first few days. As the pain subsides, you may apply heat to help improve circulation in the area. Light stretching can also boost circulation.

Shingles treatment can include antiviral drugs, such as acyclovir (Zovirax), valacyclovir (Valtrex), and famciclovir (Famvir) to knock out the virus and keep symptoms under control. If the pain is too great, capsaicin cream or numbing drugs, such as lidocaine (AneCream, LMX 4, LMX 5, RectaSmoothe, RectiCare), may be necessary.

Hidradenitis suppurativa is treated with antibiotics and acne-fighting medications. If the condition doesn’t respond to medications, surgery may be necessary.

Treatment for swollen lymph nodes depends on the cause. A bacterial infection will require antibiotics, while a viral infection will usually just need time to resolve itself. Sometimes, a warm, wet cloth applied to the affected part of the armpit may reduce the pain.

If the pain is a symptom of breast cancer, then treatment may include surgery to remove the tumor or affected lymph nodes, chemotherapy, or radiation.

Many conditions that can cause armpit pain, such as shingles or a pulled muscle, are manageable and usually temporary, lasting several days to a few weeks.

Breast cancer or problems with your lymph nodes can be life-threatening, but treatment options continue to improve survival odds. This is especially the case if the cancer is diagnosed and treated in its earliest stages.

Preventing breast cancer or lymphatic disorders may be nearly impossible. Other causes of underarm pain may be avoidable with a few precautions. For instance, you can prevent a pulled muscle by stretching and not pushing yourself beyond your abilities in the weight room.

The shingles vaccine isn’t 100 percent effective, especially as you get older, but it can greatly reduce your odds of infection by the virus. Other less-serious skin problems, such as contact dermatitis, can be prevented by switching deodorants, antiperspirant products, or detergents that might be bothering your skin.

In general, you want to practice good skin hygiene in areas that can trap oil, sweat, and dirt. Keep your armpits clean and don’t wait to see a doctor if you notice a rash or other problem.