Common causes of armpit pain include muscle strain, injuries, infections, allergic reactions and sweat rash. Rare causes include cysts, pinched nerves, autoimmune disorders and cancer.
There seems to be no conditions that would cause pain exclusively in the right or in the left armpit. Pain in both armpits can be caused by menstrual cycle or systemic infections, such as infectious mononucleosis.
Pulled Muscles and Other Injuries
Muscle strain (pulled muscle) due to arm overuse or overstretching can cause sudden pain, tenderness and mild swelling in the muscles in the front, behind or below the armpit.
Armpit pain with bruising can be caused by using crutches, wearing splints, direct hit into the armpit, rib fracture, shoulder dislocation or armpit surgery.
Serratus anterior muscle overuse can result in stabbing pain in the side of chest, shoulder blade and inside of the arm.
Pectoralis minor syndrome includes pain below the collarbone, in the armpit and upper back.
Compression of the nerves (brachial plexus) near the armpit by the neck muscles, clavicle and eventual abnormal rib (cervical rib) can cause pain, tingling or numbness in the armpit, neck, shoulder and down the inside of the arm (thoracic outlet syndrome). The condition can be caused, for example, by arm overuse in assembly workers or bad sitting posture in students (leaning forward on the elbows).
Long thoracic nerve injury on the side of the chest can result in numbness and vague mild aches below the armpit and protruding scapula (winged scapula).
Botox injections in individuals with excessive sweating (hyperhidrosis) can result in constant armpit pain.
Rib fracture usually causes sudden, sharp pain on the side of the chest (below the armpit).
Painful Lumps: Swollen Lymph Nodes
In healthy individuals, the lymph nodes usually cannot be felt with the fingers, but in some skinny persons they can appear as soft, non-tender pea-sized nodules . Lymph nodes are considered enlarged when they are bigger than 1 cm — the condition is called lymphadenopathy.
Systemic Infections with Painful Lumps in Both Armpits
Infected armpit lymph nodes (lymphadenitis) are large, hard and tender, sometimes with reddened overlying skin .
Infection by the Epstein-Barr virus (infectious mononucleosis), mainly in children and young adults, causes fever, severe fatigue, excessive sweating, sore throat and enlarged and painful lymph nodes in the neck and armpits, usually on both sides .
Toxoplasmosis, a parasitic infestation contracted by ingestion of cat feces can cause painful or painless enlarged lymph nodes in the neck and armpits, sore throat and mild fever [8,28].
Bubonic plague (mainly in Africa) and rat-bite fever (mainly in Asia) are bacterial infections that can cause sudden fever and very tender lymph nodes in the armpits [9,42].
Local Infections and Bites
A bacterial infection or venomous bite in the arm, hand or fingers can result in an infection of the lymphatic vessels (lymphangitis) with tender red streaks travelling along the inner side of the arm toward the armpit lymph nodes .
- Bacterial infections:
- Cat scratch disease can develop after a cat scratch, bite or lick .
- Tularemia (rabbit fever, deer-fly fever) is transmitted by deer fly or tick bite .
- Staphylococcal (staph) or streptococcal (strep) skin infections include boils, cellulitis and impetigo [6,7].
- Armpit abscess is a collection of pus under the skin as a complication of furuncle, hidradenitis suppurativa, injury or surgery. It appears as tender, warm, rubbery, pea-sized or up to golf ball-sized lump that can cause throbbing pain [13,17].
- Snake, spider or scorpion bite in the arm can result in sudden, painful swelling of the lymph nodes in the armpit [20,15].
Painless Hard Armpit Lumps
Epidermoid cyst appears as a pea- or marble-sized lump, which can have an opening that allows squeezing white greasy material out of it .
Lipoma is a benign tumor that contains fat tissue.
Diabetic mastopathy, mainly in women with diabetes type 1, can present with painless hard lumps in one or both breasts or armpits .
Enlarged, painless armpit lymph nodes can appear in some viral (finger herpes, measles , shingles , HIV/AIDS [9,27]), bacterial (tuberculosis, brucellosis, syphilis [9,24]) and fungal infections (histoplasmosis, sporotrichosis ).
Infantile papular acrodermatitis or Gianotti-Crosti syndrome. In children between 6 months and 12 years of age, painless, mildly enlarged lymph nodes in the armpits and groin and skin rash on the legs, arms and face that persist for several month after infection healing can appear in [7,9,10,16]:
- Viral infections: citomegalovirus (CMV), hepatitis A, B or C, herpes virus, infectious mononucleosis, parvovirus B19, rubella
- Bacterial infections: cat scratch disease, Lyme disease
- Vaccines against diphtheria, hepatitis B, influenza, measles-mumps-rubella, smallpox, pertusis and polio
Rheumatoid arthritis , systemic lupus erythematosus (SLE) , Sjögren’s syndrome, sarcoidosis [9,41] and other autoimmune diseases can present with enlarged, painless (but sometimes painful) lymph nodes in the neck, chest, armpits and groin, joint pain and skin rash [6,7,12,39].
Multiple, enlarged, fixed, hard and usually non-tender lymph nodes in the armpit can be caused by cancer [6,7]:
- Hodgkin lymphoma symptoms may include dry cough, lumps in one or both armpits, pain in the armpits and chest triggered by drinking alcohol, low-grade fever and fatigue [21,30].
- Non-Hodgkin lymphoma 
- Melanoma, a highly malignant skin cancer, appears as a dark–black, brown or blue–mole .
- Breast cancer presents with usually a non-tender lump in a breast and enlarged lymph nodes above the clavicle and in the armpit on the affected side .
- Leukemia, a cancer of white blood cells, can present with fatigue, paleness, frequent infections, enlarged lymph nodes and spleen .
- Advanced lung cancer can cause dry cough, coughing up blood, chest pain and enlarged armpit lymph nodes .
Other causes of painless lumps in armpits:
- Allergic reaction to sulfa drugs, iodine, or penicillin [6,7]
- Silicon breast implants [8,38]
Hard, painless lumps in the armpits may speak for a cancer.
Painful Armpit Rash
Itchy or burning rash in the armpits includes:
- Ingrown hair due to shaving
- Ringworm – a fungal infection
- Bacterial folliculitis
- Boil (furuncle) – a bump formed by several infected hair follicles
- Heat rash (sweat rash, miliaria)
- Fox-Fordyce disease – a rare disease with clogged sweat glands
- Irritant or allergic contact dermatitis due to deodorants or clothes
- Erythrasma – a bacterial infection caused by Corynebacterium
- Inverse psoriasis
- Hidradenitis suppurativa – a chronic inflammation and infection of the hair follicles
Armpit Pain in Women
Cyclic breast pain is dull, heavy pain in the upper outer parts of breasts and sometimes, armpits or arms on one or both side; it starts after ovulation and resolves with the onset of menstruation [3,4].
Mastitis is a breast inflammation, usually caused by an infection during breastfeeding. Symptoms include red and swollen breast on one or both sides and enlarged and painful lymph nodes in the armpit on the affected side .
Unlikely Causes of Armpit Pain
Common cold, flu, chickenpox, tonsillitis, scarlet fever, ear infection, tooth abscess, strep throat (pharyngitis), throat cancer (laryngeal or pharyngeal) or thyroid cancer can cause enlarged lymph nodes in the neck, but less likely in the armpits.
Heartburn, angina pectoris or heart attack may cause armpit pain, but not likely without typical pain behind the breastbone or in the upper back.
Hyperthyroidism and hypothyroidism do not typically cause armpit pain.
Fibromyalgia can cause pain in the neck, upper chest and back, but not likely in the armpits.
Skin tags (soft skin stalks) and warts in the armpits are usually painless .
Frequently Asked Questions
Can skin cancer appear in the armpit?
Skin cancer probably very rarely appears in the armpits. However, melanoma on the back can be associated with enlarged lymph nodes in an armpit .
Does any condition causes pain specifically in or near the right or left armpit?
In short, no. Heart-related pain is more common on the left side, but it is more likely felt in the left shoulder or upper arm than in the armpit.
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