Armpit pain is a common complaint that can have many causes, from mild muscle injuries to swollen lymph nodes and severe skin infections. In most cases, armpit pain isn't a reason to worry, but it can be a sign of a more serious underlying problem.
The armpit, also known as the axilla, is the hollow area under the junction of arm and the shoulder. Armpits are an intersection of many different anatomic structures in the body, Dr. Albert Lin, orthopedic surgeon and chief of shoulder service at University of Pittsburgh Medical Center, tells TODAY.com.
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These include the nerves, blood vessels and lymph nodes, as well as muscles and tendons that connect the chest, rib cage and wing bone to the upper arm bone, says Lin. "The ligaments that hold the shoulder joint together are near the armpit as well," says Lin.
The sensitive skin of the armpit is delicate and full of sweat glands and hair follicles. In short, there's a lot going on in our armpits — and a lot of possible things that can cause pain.
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There are many different causes of armpit pain involving various musculoskeletal structures, tissues, glands and skin in the armpit.
1. Muscle strain
Often, armpit pain is a simple case of a strained muscle.
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"The most common causes include repetitive or traumatic injuries to the muscles and tendons that insert onto the arm bone," says Lin. These include the pectoralis, or the chest muscles, the latissimus dorsi muscle, which stretches around the back to the sides and arms, and the rotator cuff.
These can be strained due to repetitive movements or overhead sports, such as swimming, volleyball and baseball, says Lin. Armpit pain can also be caused by acute injuries to muscles or ligaments during weightlifting, for example. Direct impact during contact sports can also lead to musculoskeletal armpit pain, Lin adds.
Motions where the arm moves away from the body, such as throwing, can overstretch the injured muscles and worsen symptoms.
In most cases, the pain will go away with rest, over-the-counter medication and prescribed exercises from a physical therapist, the experts note.
2. Nerve pain
There are several nerves that run through the armpit, which help provide sensation and allow movement of the upper arm. Nerve pain is usually radiating, or travels from the armpit to another part of the body, and can feel electrical in nature, Lin says.
"Occasionally stretch injuries to the nerves in the armpit can cause pain, such as during a traumatic shoulder dislocation," Lin adds. Pinched nerves in the armpit or pinched nerves coming out of the spine can also cause underarm pain.
A cold or warm compress, anti-inflammatories, and gentle massages or stretches may help with nerve-related armpit pain, Dr. Kitty O’Hare, senior medical director for pediatrics at Duke Primary Care, tells TODAY.com.
“Symptoms of numbness, tingling and radiating pain down into the hand that is associated with progressive arm weakness should be seen by a doctor right away,” says Lin.
3. Swollen lymph nodes
Lymph nodes are small glands that are part of the immune system, says O'Hare. They help the body fight off infections by acting as filters that trap and remove bacteria, viruses and other germs, per the Mayo Clinic.
They're located throughout the body in the armpits (called axillary lymph nodes), the groin, neck and chest. The nodes can become swollen and painful, usually when the body is fighting off infections.
Bacterial infections
Localized bacterial infections in the armpit or nearby can cause painful, swollen lymph nodes. These often occur when bacteria from the skin (often staphylococcus or streptococcus) enters a wound, such as a cut from shaving, says O'Hare.
Breast infections caused by bacteria, which often happen in breastfeeding women, can also cause painful lymph nodes in the armpit.
Less commonly, painful underarm lymph nodes may be caused by bacterial infections such as tuberculosis or cat scratch fever.
Viral infections
"If you're noticing multiple lymph nodes swollen, not just in the underarm, that makes us think about viral infections," says O'Hare.
Common viruses that can cause swollen, painful axillary lymph include mononucleosis, Epstein-Barr virus and influenza, she adds.
In the case of common bacterial or viral infections, the pain will usually resolve within a few days and the lymph nodes will return to normal size within a week or two, depending on the infection.
“If you’ve had a swollen lymph node for a day or two, or if it’s small and not getting worse, that is most likely to have a more benign cause,” says O’Hare.
Cancers
Rarely, painful axillary lymph nodes can be caused by cancer. These include lymphoma (cancer of the lymphatic system), breast cancer and lung cancer, says O'Hare.
“If a (swollen lymph node) has been present for a long time, or if it’s growing, that’s when we start to wonder if it might be something more serious,” says O’Hare.
4. Autoimmune disorders
Rheumatoid arthritis, an autoimmune inflammatory disease, can cause swelling and inflammation in the shoulder joint and tissues which may manifest as armpit pain, says O’Hare.
Psoriasis is a chronic, autoimmune skin condition that causes inflamed red patches of skin. "What's called inverse psoriasis can affect the armpits," Dr. Adam Friedman, professor of dermatology at the George Washington School of Medicine, tells TODAY.com. Inverse psoriasis occurs in skin folds and is worsened by friction and sweat, Friedman adds. It can cause an armpit rash that becomes raw or cracks open, which can be itchy and very painful.
5. Hormonal changes
Hormones are another possible culprit of armpit pain.
“If you still experience menstrual periods, depending on where you are in your cycle, you can feel more pain in the chest area or under the arm," says O'Hare. Pain often occurs in both armpits and may radiate from the breasts.
6. Intertrigo
Intertrigo (sweat rash) is a term used to describe inflammation in the folds of the skin, says Friedman, which is caused by friction or skin rubbing against skin and sweat. It's a common condition which often occurs in areas that are warm and moist, like the armpits, and can cause irritation, inflammation, and pain.
Intertrigo can also lead to secondary infections when bacteria or yeast gets trapped in the skin folds.
7. Contact dermatitis
Contact dermatitis is a type of rash which occurs when the skin comes into contact with an irritant or allergen. It’s one of the most common causes of painful skin irritation in the armpits, Friedman notes, often because people use so many products on the armpits to combat sweating or odor.
The skin barrier of the armpit is also more prone to damage or irritation, especially with the added friction and moisture. This can allow more irritants or allergens to penetrate and cause problems, says Friedman. A contact dermatitis rash is often red or purple and can be itchy, burning or painful, and develop blisters.
Irritant contact dermatitis
Irritant contact dermatitis results from direct skin contact with toxic materials, chemicals or other harsh substances. These include harsh soaps, detergents, cleaners or solvents. The reaction is usually immediate after exposure.
When it comes to body odor, Friedman says he's seen people use everything from baking soda to disinfectant wipes on their armpits to get rid of the smell. "Obviously, those can cause significant irritant contact dermatitis," he adds. Irritating ingredients in deodorants and antiperspirants may even cause a painful chemical burn.
Treatment involves avoiding the irritant and using creams or ointments to repair the skin barrier, says Friedman.
Allergic contact dermatitis
"Allergic contact dermatitis occurs in people who are uniquely sensitized to particular allergens, with which the skin comes into contact," says Friedman. It can take weeks or months of exposure to a substance for a person to become hyper-sensitized, and the allergic reaction can take days to appear.
Common causes of allergic contact dermatitis in the armpits include fragrances in deodorants, essential oils, dyes, shaving creams or aluminum in antiperspirants. The rash can be sore and painful.
In addition to avoiding the allergen, treatment for allergic contact dermatitis may involve topical steroids, says Friedman. A patch test is the best way to know which substances cause an allergic reaction.
8. Folliculitis
Folliculitis occurs when the hair follicles in the skin of the armpit become inflamed and infected, often due to a bacterial infection. This can cause painful, fluid-filled pimples. "It's caused more often than not by staph, and sometimes strep," says Friedman.
The infection can become severe and lead to a painful abscess of the hair follicle. Shaving or waxing are common ways people get folliculitis in their armpits, says Friedman.
9. Hidradenitis suppurativa
Hidradenitis suppurativa (HS) is a chronic auto-inflammatory disorder which causes painful nodules, boils and abscesses which primarily affects skin folds, Friedman notes. It often occurs in the armpits, groin and buttocks, near hair follicles and sweat glands.
"It can be extraordinarily, exquisitely painful ... so much so that people can't sit or they can't lift their arms up," says Friemdan. If undiagnosed and left untreated, HS has a greater likelihood of causing permanent, disfiguring scarring that can limit range of motion and cause more pain, he adds.
When to call the doctor for armpit pain
A minor, isolated ouch in the armpit is typically not a reason to worry. However, some armpit pain can be a sign of a more serious health problem, such as an infection or illness.
If the pain is severe, persistent, or accompanied by other symptoms, it may be time to seek medical attention.
“Any pain that is deep in the armpit and occurs without trauma ... and is associated with swelling, a mass, unexpected weight loss, fever, or fatigue are red flags of a more serious condition and should be brought to the attention of a doctor right away,” says Lin.
Acute armpit pain resulting from trauma or a sports injury that’s associated with a pop, rip or tearing sensation should also be checked out immediately, Lin adds.
And “symptoms of numbness, tingling and radiating pain down into the hand that is associated with progressive arm weakness should be seen by a doctor right away,” he explains.
In any case, if the pain is interfering with your daily life or activities, talk to your doctor.
This story first appeared on TODAY.com. More from Today:
