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Swollen Forearm: Causes, Symptoms & How to Treat

An arm bent at the elbow with a large bump on the forearm. Four red lines emanate from the bump.
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Last updated April 10, 2024

Swollen forearm quiz

Take a quiz to find out what's causing your swollen forearm.

Most commonly, a swollen forearm can be caused by insect bite or exposure to certain plants. Forearm swelling with pain can be caused by trauma from an injury. Read below for more information on causes and treatment options.

Swollen forearm quiz

Take a quiz to find out what's causing your swollen forearm.

Take swollen forearm quiz

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Swollen forearm symptoms

Whether your sleeve feels more snug than usual, or you can see that one of your forearms looks a bit puffy, forearm swelling can be a cause for concern. Swelling occurs whenever the parts of the body enlarge due to an accumulation of fluid in the body tissues. Swelling can be generalized and occur throughout the body, or localized and only affect a specific part of the body, such as the forearm.

Common characteristics of a swollen forearm

Localized swelling is more common, and in the case of a swollen forearm, the swelling may be difficult to ignore. Swelling in the forearm can be associated with:

Swelling in the forearm requires medical attention in part because it is an uncommon symptom.

Swollen forearm causes

Even though the forearm has multiple components, forearm swelling is usually the result of damage or inflammation to the muscles and bones.

Forearm structure

The bones of the forearm include the radius, which starts at the elbow and connects at the wrist on the thumb side, and the ulna, which starts at the elbow and connects at the wrist on the pinkie side. See this image for a visual representation. The forearm contains multiple muscles that turn the forearm/hand upwards (supination) and downwards (pronation) but and also flex and extend the digits of the hand.

Traumatic causes

Traumatic causes of a swollen forearm may include the following.

  • Fracture: Anything that causes direct injury to the forearm, such as a car accident, a traumatic fall, a direct blow, can result in broken bones in the forearm, resulting in swelling and pain. These causes may also be associated with visible deformity and bleeding depending on the severity of the trauma.
  • Sprain: A sprain is defined as twisting or stretching of a ligament or tendon. A ligament is a band of connective tissue that connects bone to bone. A tendon is also a band of connective tissue, but it connects muscle to bone. The forearm has multiple ligaments that can be sprained in activities that cause bending, twisting, sudden movement or direct impact.

Environmental causes

A bite from an insect, such as a mosquito, spider, etc., can cause the forearm to swell and also become itchy and painful.

Cancerous causes

Cancers can specifically target the bones of the forearm. The body's lymphatic system (the system that filters excess fluid and fights infection) can become blocked, causing fluid to build up. This phenomenon is known as lymphedema and often affects the arms or legs.

This list does not constitute medical advice and may not accurately represent what you have.

Non-specific forearm pain

Forearm pain can be caused by a host of things, but is often idiopathic (without cause).

Your forearm pain is normal and unlikely to be caused by a serious illness. You can try over the counter pain medication like Tylenol. If the pain becomes severe, see a physician.

Insect bite on the arm

Insect bites are very common. They often cause itchiness, redness, and some swelling. Most insect bites can be treated at home.

Rarity: Common

Top Symptoms: swollen forearm, mild forearm pain, forearm bump, forearm redness, forearm itch

Symptoms that never occur with insect bite on the arm: fever, worsening forearm redness, severe forearm pain, high-pitched breathing, wheezing, racing heart beat

Urgency: Self-treatment


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

Carpal tunnel syndrome

Carpal tunnel syndrome causes numbness and pain in the underside of the wrist and hand. It is caused by narrowing of the carpal tunnel passageway, which puts pressure on the nerve running through it.

Narrowing and deformity of the tunnel is most often from overuse, especially highly repetitive activities such as typing or working on an assembly line. Wrist fracture or arthritis can damage the carpal tunnel, and so can diabetes and obesity.

Symptoms include numbness and shocklike pain in the wrist, palm, and fingers. There may be weakness in the hand when trying to hold an object.

Carpal tunnel syndrome virtually always gets worse over time. Permanent damage may result, so it is important to be seen by a medical provider.

Diagnosis is made through patient history and physical examination. X-rays or electromyography testing may be used.

Rest and cold packs to the wrist will reduce swelling. Wrist splints and ergonomically correct keyboards and other devices during work are often helpful.

Corticosteroid injections and surgery may also be tried.

Buckle fracture of distal radius

A buckle fracture of the wrist, also known as a torus fracture, is a condition that are most common in children aged 5-10 years due to the elasticity of their bones. This fracture occurs when force is applied to the radius (one of the two bones of the forearm), causing the bone to split along the growth plate.

You should visit your primary care physician within the next 24 hours. The treatment for this kind of fracture is immobilization in a cast.

Rarity: Common

Top Symptoms: constant forearm pain, forearm pain from an injury, pain in one forearm, swollen forearm, wrist injury

Symptoms that always occur with buckle fracture of distal radius:forearm pain from an injury, constant forearm pain

Urgency: Primary care doctor

Bruised forearm

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 forearm are common, often due to minor injuries.

You can treat this at home with R.I.C.E - rest (exercise as tolerated), ice (10-20 minutes at a time), compression (with tape or bandage), and elevation.

Rarity: Uncommon

Top Symptoms: constant forearm pain, pain in one forearm, forearm pain from an injury, forearm bruise, swelling of one forearm

Symptoms that always occur with bruised forearm: forearm pain from an injury, constant forearm pain

Urgency: Self-treatment

Acute forearm bone infection (osteomyelitis)

Osteomyelitis of the forearm is a bacterial or fungal infection of the 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: moderate fever, spontaneous forearm pain, constant forearm pain, warm and red forearm swelling, painful surgical site

Symptoms that always occur with acute forearm bone infection (osteomyelitis): spontaneous forearm pain, constant forearm pain

Urgency: Hospital emergency room

Swollen forearm treatments and relief

If your symptoms are due to a traumatic cause, promptly make an appointment with your physician in order to assess for serious injury. In the meantime, use the RICE method to help alleviate your symptoms.

  • Rest: Limit movement and use of the affected forearm as much as possible.
  • Ice: Put an ice pack on your forearm every 15 minutes in order to reduce swelling.
  • Compression: Protect your forearm from excessive movement by using a compression wrap or tape. Compression can also help reduce swelling.
  • Elevation: Raising your forearm above your heart can also help reduce swelling.

Medical treatments

If your forearm swelling is due to trauma or malignant causes, your physician may suggest:

  • Immobilization (sling): After a traumatic injury, your physician may provide a sling to keep your forearm from moving.
  • Physical therapy or rehabilitation: Your physician may prescribe stretching exercises or a physical therapy program to help you restore function to your forearm, especially after an injury.
  • Chemotherapy or radiation: If your symptoms are due to malignant disease, your physician will discuss options such as surgery, radiation, or chemotherapy with you depending on the specifics of your condition.

Questions your doctor may ask about swollen forearm

  • Any fever today or during the last week?
  • Is your swollen area warm and red?
  • Do you notice your heart beating hard, rapidly, or irregularly (also called palpitations)?
  • How would you explain your forearm pain?

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

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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.
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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