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What Causes Swelling of One Arm? Your Questions Answered

An illustration of an arm coming at a diagonal upwards angle from the right side. The hand is relaxed, and there is a large bulge just below the wrist. Four red lines come from the top of the bulge, and three from below. The skin is medium-dark peach-toned.
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When you notice one arm is suddenly bigger, it can cause immediate concern. In most cases, the reason is because of trauma from an injury or repetitive strain. Other causes include deep vein thrombosis, a bone infection, and cellulitis. Learn more about what causes just one arm to become swollen and the best way to treat.

8 most common cause(s)

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Bone Infections
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Deep Vein Thrombosis
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Repetitive Strain Injury of the Upper Arm or Shoulder
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Benign bony growth (osteochondroma)
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Bruised tricep
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Bicep bruise
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Compartment syndrome

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Swollen arm symptoms

Since the arms are used for so many activities of daily life, it's unlikely any problems will go unnoticed. Swelling of one arm can interfere with your mobility and strength, particularly if other symptoms like pain are also present. There are multiple types of structures that drain fluid out of the arm: the venous system drains blood on its way back to the heart, and the lymphatic system drains cellular waste fluid. Blockage of the venous or lymphatic system in one arm can cause a backup of fluid, leading to swelling. Problems with the elbow joint can also cause swelling.

Common characteristics of swelling of one arm

Depending on the cause, arm swelling can be associated with the following additional symptoms:

8 swelling of one arm causes

What causes arm swelling?

Swelling of one arm is typically caused by a local problem since systemic diseases associated with swelling will affect both arms and likely other parts of the body. Unilateral arm swelling can result from a problem with venous or lymphatic drainage; a local infection or inflammatory reaction; or an injury.

Venous problems

Problems in the veins can lead to swelling of one arm, such as the following.

  • Blood clot: A clot in one of the deep veins (deep vein thrombosis or DVT) of the arm can cause swelling, often accompanied by pain and redness. Arm clots are uncommon but can occur in the setting of vascular trauma, such as when a pacemaker or catheter is present. A clot may be complicated by chronic arm swelling.
  • Compression: Compression of the large subclavian vein near the neck can obstruct venous drainage, leading to swelling and blue discoloration of the arm. Tingling in the fingers is often present due to hand swelling and/or nerve compression. Anatomic abnormalities such as an extra rib are the primary cause. Subclavian vein compression is the primary cause of deep venous clots in the arm in the absence of catheters or other devices.

Lymphatic problems

Damage to the arm's lymphatic drainage system or mechanical blockage can cause a backup of lymph fluid (lymphedema). Tumors, lymph node surgeries, and certain infections can cause lymphedema and swelling in one arm. Removal of lymph nodes in the armpit as part of breast cancer treatment is a particularly common cause of upper extremity lymphedema.

Inflammatory reaction

Inflammatory causes can lead to swelling of one arm, such as the following.

  • Vaccination: Rarely, swelling of the arm can be observed after receiving multiple doses of a childhood vaccine (DTaP).
  • Insect bites: Most people will experience some degree of swelling with an insect bite on the arm. Those who have an allergy can have a larger amount of swelling, extending as much as 10 inches beyond the site of the bite.

Injury-related causes

Injuries can result in swelling of one arm in regards to the following.

  • Overuse injuries: Biceps tendonitis and acute injuries such as a fracture can cause swelling of the arm along with pain.
  • Chronic pain syndrome: An injury to the arm can be followed by a chronic pain syndrome characterized by pain, swelling, abnormal temperature sensation, and changes in the appearance of the skin.


An infection of the skin and deeper tissues of the arm will result in swelling, redness, and warmth.

Repetitive strain injury of the upper arm

Repetitive strain injury of the upper arm is caused by consistent repetitive use.

You do not need treatment, just rest from your overuse. Wearing a brace and physical therapy might be helpful.

Rarity: Uncommon

Top Symptoms: upper arm pain from overuse, upper arm weakness, upper arm numbness

Symptoms that always occur with repetitive strain injury of the upper arm: upper arm pain from overuse

Symptoms that never occur with repetitive strain injury of the upper arm: upper arm injury, severe upper arm pain

Urgency: Self-treatment

Deep vein thrombosis

A deep vein thrombosis (DVT) occurs when a blood clot forms in a vein deep in the body, usually in the lower leg or thigh. DVT can cause swelling, pain, and redness in the affected leg. Some of the risk factors for developing DVT include obesity, pregnancy, cancer, surgery, and previous history of blood clots.

You should consider calling your primary care or urgent care provider. Deep vein thrombosis can be evaluated with a review of your symptoms, a physical exam, and an ultrasound. A blood test may also be performed. Once diagnosed, DVT can be treated with blood-thinning medication, which is usually taken for three months.

Rarity: Uncommon

Top Symptoms: fever, thigh pain, upper leg swelling, calf pain, butt pain

Urgency: Hospital emergency room

Compartment syndrome

Acute compartment syndrome describes the damage done to certain muscle groups of the arms or legs after a traumatic injury.

All of the long muscles are bundled into sections – "compartments" – by the white sheets of strong, tough connective tissue called fascia. If something interferes with circulation so that blood flow is trapped within the compartment, pressure rises because the fascia cannot stretch. This causes serious damage to the muscles and other tissues within the compartment.

Acute compartment syndrome is caused by a broken bone; a crush injury; burns, due to scarred and tightened skin; and bandages or casts applied before an injury has stopped swelling.

Symptoms can rapidly intensify. They include severe pain and tightness in the muscle; tingling or burning sensation; and sometimes numbness and weakness.

Acute compartment syndrome is a medical emergency which can result in loss of the limb. Take the patient to the emergency room or call 9-1-1.

Diagnosis is made through patient history and physical examination.

Treatment involves hospitalization for emergency surgery and, in some cases, skin graft.

Rarity: Rare

Top Symptoms: arm numbness, hand numbness, foot numbness, pain in one leg, thigh numbness

Urgency: Hospital emergency room

Chronic upper arm bone infection (osteomyelitis)

Osteomyelitis of the thigh, or thigh bone infection, is a bacterial or fungal infection of the thigh bone, typically caused by Staph Aureus (40-50% of the time). It is difficult to diagnose as the infection can come from a break in the skin at the area or anywhere else in the body that spreads by blood.

You should seek immediate medical care at an ER, where diagnosis of osteomyelitis can be established through x-rays and culturing fluids. Treatment involves antibiotics and removing the infected tissue (by surgery).

Rarity: Rare

Top Symptoms: spontaneous shoulder pain, moderate fever, painful surgical site

Symptoms that always occur with chronic upper arm bone infection (osteomyelitis): spontaneous shoulder pain

Urgency: Hospital emergency room


Cellulitis is a bacterial infection of the deep layers of the skin. It can appear anywhere on the body but is most common on the feet, lower legs, and face.

The condition can develop if Staphylococcus bacteria enter broken skin through a cut, scrape, or existing skin infection such as impetigo or eczema.

Most susceptible are those with a weakened immune system, as from corticosteroids or chemotherapy, or with impaired circulation from diabetes or any vascular disease.

Symptoms arise somewhat gradually and include sore, reddened skin.

If not treated, the infection can become severe, form pus, and destroy the tissue around it. In rare cases, the infection can cause blood poisoning or meningitis.

Symptoms of severe pain, fever, cold sweats, and fast heartbeat should be seen immediately by a medical provider.

Diagnosis is made through physical examination.

Treatment consists of antibiotics, keeping the wound clean, and sometimes surgery to remove any dead tissue. Cellulitis often recurs, so it is important to treat any underlying conditions and improve the immune system with rest and good nutrition.

Rarity: Uncommon

Top Symptoms: fever, chills, facial redness, swollen face, face pain

Symptoms that always occur with cellulitis: facial redness, area of skin redness

Urgency: Primary care doctor

Bruised tricep

A bruise is the damage of the blood vessels that return blood to the heart (the capillaries and veins), which causes pooling of the blood. This explains the blue/purple color of most bruises. Bruises of the tricep are common, often due to minor injury.

You can treat this at home with rest (exercise as tolerated) and ice (10-20 minutes at a time).

Rarity: Rare

Top Symptoms: constant upper arm pain, tricep injury, pain in one tricep, swelling of one arm, upper arm bruise

Symptoms that always occur with bruised tricep: tricep injury, constant upper arm pain

Urgency: Self-treatment

Bicep bruise

A bruise is the damage of the blood vessels that return blood to the heart (the capillaries and veins), which causes pooling of the blood. This explains the blue/purple color of most bruises. Bruises of the bicep are common due to minor injuries.

You can treat this at home with rest (exercise as tolerated) and ice (10-20 minutes at a time).

Rarity: Rare

Top Symptoms: constant upper arm pain, recent bicep injury, pain in one bicep, swelling of one arm, upper arm bruise

Symptoms that always occur with bicep bruise: recent bicep injury, constant upper arm pain

Urgency: Self-treatment

Benign bony growth (osteochondroma)

An osteochondroma is a non-cancerous growth that usually develops during childhood or adolescence. It is a benign tumor that forms on the surface of a bone near the growth plate.

You should visit your primary care physician for X-Ray evaluation. In most cases this condition is treated by careful observation over time to make sure the tumor does not grow. Surgery is considered if the osteochondroma causes pain, puts pressure on a nearby nerve or blood vessel, or has a large cap of cartilage.

Rarity: Ultra rare

Top Symptoms: lower leg bump, upper leg bump, numbness in one thigh, painful thigh lump, hip bump

Urgency: Primary care doctor

Swollen arm prevention, at-home treatments, and professional treatments

The treatments for arm swelling vary since there are many different causes. Treatment options may also target associated pain. Understand your risk factors for certain conditions and possibly take the steps below to prevent them.


There are methods of preventing swelling of one arm that can be coordinated between you and your medical provider.

  • Biopsy for cancer: Starting with a biopsy rather than lymph node removal for breast cancer staging and treatment leads to lower rates of arm lymphedema.
  • Avoid injected drug use: This behavior is a risk factor for clots and infections. If you do inject drugs, use clean needles and inject intravenously rather than into the skin or muscle, which will decrease the risk of infection.
  • Reduce clot risk: If you have any history of clots, avoid drugs containing estrogen, which will increase the risk of recurrent clots. Avoid smoking, which also contributes to clot risk.

At-home treatments

Some treatment methods for swelling of one arm can begin at home.

  • Pain medication: Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin) are effective for pain associated with venous compression, injuries, and chronic pain syndrome.
  • Antihistamines: Benadryl, for example, will help alleviate the swelling and itching associated with insect bite reactions.
  • Rest and ice: Initial rest and icing followed by strengthening activities can help with overuse tendonitis.

Medical treatments

Medical treatments, such as the following, can be recommended after proper consultation with your physician.

  • Anticoagulation medication: This medication inhibits clot formation and is the best treatment for an arm clot. In some cases, a thrombolytic (medication to break up a clot already present) may also be used.
  • Surgery: This may be required to repair anatomic abnormalities causing venous compression or for tendon overuse injuries when other treatments have failed.
  • Antibiotics or drainage: An infection will require antibiotics and possibly drainage of infected fluid.
  • Massage and compression: Blocked lymphatic drainage can be partially improved with massage and compression, as well as addressing underlying causes like an infection or a tumor.
  • Other medications: Steroids and multiple types of pain medications, including antidepressants and antiepileptic drugs used for nerve pain, can help mitigate chronic pain syndromes.

When it is an emergency

You should seek care immediately if you experience the following.

  • Fever, drainage of a wound, and a spreading red or black/blue color of the skin
  • Shortness of breath and chest pain: This may indicate that a clot has dislodged from the arm and entered a lung (pulmonary embolism or PE).
  • Extreme pain and blue discoloration of the arm: This may indicate venous backup so severe that arterial blood flow is also blocked.

FAQs about swelling of one arm

Can a swollen arm be a sign of infection?

Yes, a swollen arm may indicate an infection. Redness, warmth, and drainage may also occur. Some types of infection will cause blackened skin. Animal bites, intravenous drug use, and other types of injuries that break the skin are risk factors for infection. Seek emergency care if you have rapidly spreading skin changes or signs of systemic illness such as fever [13,14].

Why does one of my arms swell after activity?

Swelling after an activity, particularly a repetitive activity like throwing, can be a sign of venous compression by an abnormality such as an extra rib. You may also notice pain and/or a red or blue appearance on the arm. It is important to receive medical attention if you notice swelling and other changes in your arm after activity since a clot can occur as a complication of venous compression [1-3,12,15].

Why do I have swelling in just one arm?

Many systemic medical conditions can cause swelling of both arms and/or legs while swelling of just one arm indicates a problem on that side. The swelling may be due to infection, particularly if it is localized to one area. It can also be caused by an acute or chronic injury. In addition, a structural abnormality of just one arm can cause swelling if it limits fluid drainage, either in the veins or in the lymphatic system [1,4,13,15].

What treatments are available for a chronically swollen arm?

Arm swelling that persists over time is often caused by a problem with venous or lymphatic drainage. Compression can help reduce swelling in both of these conditions. Additional treatments like massage and exercise can also be effective for lymphatic blockage. Surgery can be required for chronic swelling, but other treatments are typically tried first [4,12,16].

How can I tell if an insect bite on my arm is infected?

An insect bite is often followed by a small amount of swelling along with itching and redness. Some people develop more extensive reactions at the site of the bite, with a larger area of swelling, redness, and warmth. These large reactions can appear similar to a skin infection. However, the large inflammatory response to a bite starts quickly and peaks in about half a day. If the bite is complicated by an infection, symptoms will worsen after a few days [17].

Questions your doctor may ask about swelling of one arm

  • Did you just suffer from a high impact injury (e.g., a fall, collision, accident or sports trauma)?
  • Any fever today or during the last week?
  • Does your calf feel very tense?
  • Have you suffered from a burn?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

Hear what 1 other is saying
Once your story receives approval from our editors, it will exist on Buoy as a helpful resource for others who may experience something similar.
The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Swelling after heart surgeryPosted December 5, 2019 by S.
I am a 72-year-old male. Underwent open-heart surgery 4 months ago. For the last 2 months I have swelling at different parts of my body. Especially on the arms and legs and back of my body. Suddenly, affected area starts swelling, become red and hot. I consulted 4/5 doctors. They gave me anti-allergy medicine and ointment, which had no effect and give any relief. It starts any time, anywhere and goes back after few days. But no pain, swelling only.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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