Causes of Armpit (Underarm) Pimples, Sores and Lumps

Pimples, sores and lumps under the arms are not uncommon as is itching which often occurs for no obvious reason. These lesions and symptoms may resolve on its own in many instances without any need for treatment. However, persistent pimples and sores, as well as painful lumps that are enlarging, are often a cause for concern. The latter is in many instances associated with cancer although enlarged axillary lymph nodes can occur for various reasons.

Armpit Lesions

The armpit (axilla) is a hollow created at the point where the chest wall, upper arm and shoulder meet. The overlying skin has coarser hair in adults and due to the warmth generated in this region, it tends to sweat more than other sites. There are six groups of lymph nodes in the axilla that drain lymph from the chest wall including the breasts, upper part of the abdomen and the arm.

Armpits of a woman

Armpit Pimples

The word ‘pimple’ is often used loosely to describe any tiny raised lesions (bump) on the skin surface. Usually the word is associated with acne but may also refer to tiny boils (abscesses) and cysts on or just under the skin.

Armpit Sores

Sore is another word that is used loosely to describe a range of different lesions, including boils, cysts, scabs and wounds. Most of us refer to a skin lesions as a sore when it is painful or tender or was or still is a site of bleeding.

Armpit Lumps

Lumps usually refers to large masses than pimples that is typically under the skin. Often these masses are enlarged lymph nodes and features such as whether it is hard or soft, mobile or fixed as well as if it is enlarging are important to note.

Causes of Armpit Lesions

Any lesions on the skin of the armpits or just underneath it should be assessed by a medical professional especially if it is worsening, itching or paining intensely and causing other symptoms like unusual odors. These armpit lesions may be accompanied by other symptoms like burning armpits. Although many of these lesions appear similar to many people, there are distinct difference that may indicate the underlying cause.


Itchy armpits is not an uncommon symptom. Given the hair, sweat, skin oils and lack of ventilation there may be occasional itching despite a lack of any skin disease. Aggressive scratching of the skin can easily injure it. Having long nails or jagged nails may injure the skin easily and more extensively. It can further lead to bacterial skin infections as dirt under long nails and bacteria from the mouth on bitten nails are introduced into the skin tears.

Hair Removal

Removing hair from the armpits is a commonly practiced cosmetic procedure, especially among women. The choice of hair removal can sometimes irritate the skin, lead to bacterial infections or even injure the skin and underlying tissue. Sometimes the armpit hair itself can become infected, which is a condition known as armpit trichomycosis.

In some people it may elicit an allergic reaction. Hair removal should be done carefully as the skin of the armpits do not have the same underlying support as the skin around it. Always keep the area clean and never scratch the armpits after hair removal.

Contact Dermatitis

Contact dermatitis is a common skin condition where there is inflammation and itching of the skin caused by contact with certain substances. Some of these substances can irritate any person’s skin and caused irritant contact dermatitis. Examples of irritants include water, sweat, soap and powders. Other substances only affects people who have a hypersensitivity to it and this is known as allergic contact dermatitis. Examples of allergens include certain perfumes or deodorants and waxes used for hair removal.


Folliculitis is another fairly common condition where the hair follicles become inflamed. Usually this inflammation is a result of an infection and bacteria like Staphylococcus aureus are the more common pathogen. Folliculitis can occur on healthy skin as well but in the vast majority of cases it occurs when there is a break in the skin or damage to the hair follicle. This may arise after hair removal or with scratching the area among other ways.


Ringworm is a common term used to describe fungal infections of the skin. It is called a ringworm due to the round red lesions that it causes but it is not caused by a worm. Most fungal skin infections are caused by dermatophytes and sometimes yeasts can also be responsible. The warm, dark and moist environment of the armpits provide an ideal environment for fungi and it is further promoted by skin injury.


Lymphadenitis is inflammation of the lymph nodes and often this arises during an infection. The inflammation leads to swollen armpit lymph nodes. The enlargement is usually temporary and often due to an infection in the area. However, the armpit lymph nodes can also swell when there is a systemic infection. With infections like HIV, the inflammation can be persistent for long periods of time. Sometimes the lymph node itself may become infected.


Lipomas are abnormal growths of fat tissue. It is considered as a benign tumor and the armpits are among the more common sites where lipomas occur. The exact reason why these fatty growths arise is not clearly understood but it appears to be associated with injury to the area and is also more likely to occur in people who are obese. Lipomas under the arms do not pose any significant health risk.


Enlargement of a lymph node can occur with cancer even if the lymph node itself is not affected. The cancer cells may disseminate from its original site where it developed and travel through the lymphatic vessels to other sites. The function of the lymph nodes is to identify these cancerous cells and destroy it. Sometimes the lymph node itself is affected by cancer (primary lymphoma). Breast cancer is one of the types of cancer where the armpit lymph nodes become enlarged but other cancers may also be responsible.

Skin Tags and Warts

Skin tags, medically known as acrochordons, are benign protrusions from the skin. These tags can occur anywhere on the body and the neck and armpits are commonly affected sites. Skin tags are not the same as warts although these lesions may appear similar. With warts there is abnormal growth of the skin cells often due to an infection with the human papilloma virus (HPV).

skin tag


  1. Armpit lump. MedLine Plus
  2. The armpit. WebMD

Last updated on August 18. 2018.

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