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Pain under the left armpit can be concerning, and many people associate any pain on the left side of their body with a heart attack. However, most of the time, pain under the left armpit has a less serious cause.

The armpit is a complex meeting point for muscles and connective tissues, lymph nodes, and blood vessels. As such, many issues in this area can lead to pain.

Causes range from pulled muscles and mild allergic reactions to more severe issues, such as an underlying infection.

While many of the causes of left armpit pain are not harmful in the long term, anyone experiencing breathing difficulties and pain in their chest, jaw, or neck should see a doctor immediately.

Causes of left armpit pain include:

A pulled muscle

Many muscles around the shoulder and armpit can cause pain if a person injures them.

People can pull a muscle when reaching for an object, twisting incorrectly, or overstretching.

People who exercise regularly, especially those who do weight training, may be more likely to experience muscle pulls and strains.

In these cases, the pain should go away over time, as long as the individual rests the injured muscle and does gentle stretches.

If the pain does not go away after about a week, it is best to see a doctor.

Allergic reactions

Armpits are a frequent location for allergic reactions, which could cause pain under the left armpit or both armpits.

Most allergic reactions in this area will occur due to chemicals people apply to their bodies or clothes that touch the armpits.

Possible allergens include:

  • detergent
  • fabric softener
  • soap
  • deodorant
  • perfume
  • shaving cream
  • moisturizing creams or lotions

These products may contain chemicals or perfumes that irritate the skin. A rash may also form.

Anyone who suspects that their skin is sensitive to a particular allergen should note the products they used that day and report them to a dermatologist.

Allergy testing may help find the irritating product. Avoiding products with any harsh chemicals or other ingredients can also improve symptoms in these cases.

Cosmetic procedures

Simple cosmetic procedures, such as shaving or waxing, can also be to blame for pain under the armpit. These hair removal techniques may lead to other issues, such as ingrown hairs, cysts, or general irritation and chafing in the armpit.

Skin infections

A skin infection under the armpit may cause itching and pain. Bacteria thrive in warm, damp environments such as the armpits.

An overgrowth of bacteria in this area may lead to an infection, which could cause redness, swelling, and pain, among other symptoms.

Other forms of infection, such as fungal infections due to ringworm or yeast, may also cause similar pain and irritation in the area.

Mild skin infections should clear up without treatment if a person keeps the area clean and dry. However, a doctor may recommend antibiotic creams or medications to treat more severe cases.

Hidradenitis

Hidradenitis is a chronic condition that causes similar symptoms to severe acne. Hidradenitis occurs due to clogged hair follicles and glands. It is common in areas such as the armpits, where the skin rubs together.

Hidradenitis can lead to multiple cysts or boils developing in the area. In addition to these breakouts, the person will likely experience pain and tenderness.

Doctors can treat hidradenitis with anti-inflammatory medications. Some cases may require surgery.

Varicella zoster virus

The varicella zoster virus causes chickenpox and shingles. Breakouts of both illnesses are possible under the armpits, although chickenpox usually beginsTrusted Source on the face, back, and chest.

A shingles rash usually developsTrusted Source as a single strip on one side of the face or body, left or right. A person with shingles may also experience:

  • a fever
  • headaches
  • chills
  • an upset stomach

A person may feel pain and tingling in the area before the visible rash develops.

A doctor may prescribe antiviral medications to speed up the healing process, as well as pain medications to help ease symptoms.

Swollen lymph nodes

Lymph nodes are small, bean shaped bundles of tissue that play a vital role in the immune system. Lymph nodes help filter toxins from the lymph and deliver white blood cells to help fight disease.

The armpit houses a large number of lymph nodes. Lymph nodes swell as part of an overall reaction by the immune system, such as to an infection or illness.

Swollen lymph nodes in the armpit may cause:

  • a single or multiple lumps
  • tenderness
  • pain

If the swelling does not go down after an infection, such as the common cold, goes away, or the person is not feeling any other symptoms, they should speak to a doctor.

Psoriasis

Psoriasis is an autoimmune condition that leads to an overgrowth of skin cells. The buildup of skin cells forms patches called plaques. These plaques can cause symptoms such as itching and pain.

Psoriasis plaques can form anywhere, including the armpit. Some forms of psoriasis are more common in this area, including inverse psoriasis.

Psoriasis treatment typically includes both topical and oral medications to control symptoms.

Nerve damage

Nerve damage may also cause pain under the armpit. Nerve damage can be the result of a physical injury, such as one from overuse during sports or from an accident or fall.

Nerve damage can feel like:

  • pain
  • tingling
  • numbness
  • burning

Certain conditions, such as diabetes, may also lead to nerve damage or neuropathy. The National Institute of Diabetes and Digestive and Kidney Diseases note that up to half of people with diabetes have peripheral neuropathy, which is nerve damage.

While peripheral neuropathy typically affects the feet and legs, it may also affect the arms in some individuals. Diabetes treatment may help slow nerve damage progression.

Angina

Angina occurs due to a lack of oxygen-rich blood flow to the heart. This can be because one of the arteries leading to the heart is narrow or blocked.

Angina causes chest pain and discomfort, which is sometimes severe. It may also cause pressure and pain in other areas, including the:

  • armpits
  • shoulders
  • back
  • neck
  • jaw

Some people may also experience a feeling similar to indigestion.

Angina is a symptom of an underlying heart condition, for example, coronary heart disease, which can lead to a heart attack.

There are also many other types of angina. Anyone who suspects they have angina should talk to their doctor.

Cancer

In rare cases, pain under the left armpit that does not go away may be a sign of a cancerous growth, including breast cancer.

Cancer can cause the lymph nodes under the armpit to swell painfully. An individual may notice a lump under their arm or in their armpit that causes persistent pain or discomfort.

Underarm pain may also be the result of a specific cancer treatment, such as lymph node removal or mastectomy.

Anyone noticing texture changes or lumps in their chest or breast tissue should seek medical attention.

Treatment options for cancer will depend on its stage, which refers to how much it has spread. In general, earlier stages are easier to treat.

When to see a doctor

Anyone noticing the following symptoms along with left armpit pain should seek immediate medical attention:

  • shortness of breath
  • dizziness
  • pain in the chest, jaw, or shoulder

A doctor can also diagnose and treat pain from other issues, such as infections or swollen lymph nodes.

Pain under the left armpit from sources such as a pulled muscle should go away within about a week in most cases. Anyone who experiences symptoms beyond this time frame should see a doctor for a full diagnosis.

Summary

There are many possible causes of pain under the left armpit. The person may have pulled a muscle or may have swollen lymph nodes from an infection.

Other causes can be more serious, such as angina. Anyone concerned about their symptoms should see a doctor for a full diagnosis and treatment.

A new study adds to the evidence that sleep deprivation has a significant effect on our day-to-day functioning. The authors warn that if we have slept poorly overnight, we are twice as likely to commit errors, some of which may well be very costly.

Having a good night’s sleep is key to maintaining both physical and cognitive health. Our bodies know this instinctively, and researchers have proved many a time that this is true.

For example, at Medical News Today, we have covered studies showing that sleep protects vascular health, helps maintain brain health, and may even give the immune response a boost.

Conversely, poor sleep may lead to cardiovascular disease, contribute to depression, and increase a person’s risk of diabetes.

Some researchers have also warned that sleep loss can affect aspects of our memory and visual perception so severely that driving after a sleepless night can be as dangerous as drunk driving.

Following on from such evidence, researchers from Michigan State University’s Sleep and Learning Lab in East Lansing have conducted further research on sleep, attention, and higher order cognitive functioning.

Their findings, which feature in the Journal of Experimental Psychology: General, show that sleep loss has an important effect not just on how well we can maintain our focus, but also on how well we can follow complex procedures — an aspect that they refer to as “placekeeping.”

For their study, the investigators recruited 138 participants, whom they split into two groups: 77 people stayed in the laboratory overnight and had no sleep, while the remaining 61 participants slept at home.

The evening before, all of the volunteers took part in two tasks. The first one measured their reaction time to a particular stimulus, and the second one assessed their place keeping abilities — that is, how well they were able to follow the particular steps of a complex process even with repeated interruptions.

On the morning after, each participant had to repeat these tasks to see how their performance compared with that of the previous evening. The researchers found that the participants who had experienced sleep deprivation struggled significantly.

“Our research showed that sleep deprivation doubles the odds of making place keeping errors and triples the number of lapses in attention, which is startling,” says study co-author Kimberly Fenn.

“Sleep-deprived individuals need to exercise caution in absolutely everything that they do and simply can’t trust that they won’t make costly errors. Oftentimes — like when behind the wheel of a car — these errors can have tragic consequences,” she warns.

Although it may not come as a surprise that lack of sleep reduces a person’s ability to focus, the researchers note that their recent study shows that sleep deprivation actually affects higher cognitive functioning, interfering with memory recall to a large extent.

“Our findings debunk a common theory that suggests that attention is the only cognitive function affected by sleep deprivation,” says first author Michelle Stepan.

“Some sleep deprived people might be able to hold it together under routine tasks, like a doctor taking a patient’s vitals. But our results suggest that completing an activity that requires following multiple steps, such as a doctor completing a medical procedure, is much riskier under conditions of sleep deprivation.”

Michelle Stepan

“After being interrupted [as they were performing complex tasks], there was a 15% error rate in the evening, and we saw that the error rate spiked to about 30% for the sleep deprived group the following morning,” notes the first author.

“The rested participants’ morning scores were similar to the night before,” she adds. This finding, the investigators argue, should serve as a warning to people who experience sleep loss not to underestimate the effect that it can have on their daily lives.

“There are some tasks people can do on autopilot that may not be affected by a lack of sleep. However, sleep deprivation causes widespread deficits across all facets of life,” Fenn emphasizes.