Arm Swelling: Causes and When to Worry

What arm swelling looks and feels like

A swollen arm may look bigger than the other side, make rings, watches and sleeves feel tight, and feel heavy or stiff when you bend the elbow or make a fist. Doctors look at four features that narrow the cause quickly:

• Pitting or not: pressing a thumb into the skin for 5 seconds leaves a dent in pitting edema (fluid). Firm, non-pitting swelling suggests long-standing lymphedema, thyroid disease or tissue inflammation.
• Color and warmth: red and hot points to infection or inflammation. Bluish or purple with prominent veins points to a vein blockage. Bruised points to bleeding.
• Speed: swelling over minutes to hours suggests injury, allergy, infection or a clot. Swelling over weeks to months suggests lymphedema or a body-wide condition.
• Where: the whole arm, only the hand and forearm, a single joint such as the elbow, or a localized knot.

Causes of swelling in one arm

Injury and overuse

Sprains, muscle strains, fractures and bruises cause swelling within hours, usually with pain, bruising and limited movement. A heavy weight or hard workout can also cause short-lived puffiness. Bleeding into the muscle (a hematoma) can form a firm, tender knot, especially in people taking blood thinners.

Infection

Cellulitis is a bacterial skin infection that causes a spreading, red, warm, tender and swollen area, often starting from a cut, bite, scratch, injection site or crack in the skin. An abscess is a collection of pus that feels like a painful, soft or fluctuant lump. A red streak running up the arm toward the armpit means the infection is spreading along lymph vessels (lymphangitis) and needs prompt antibiotics.

Blood clot in an arm vein

Deep vein thrombosis is much less common in the arm than in the leg, but it does happen. Typical clues are swelling of the whole arm, a dull ache, a bluish tinge, and visible veins over the shoulder or chest. Risk factors include:

• a PICC line, central venous catheter, pacemaker or defibrillator leads
• cancer and its treatment
• repetitive, vigorous overhead arm activity (weightlifting, swimming, baseball pitching), which can compress the vein under the collarbone. This is effort thrombosis or Paget-Schroetter syndrome, a form of thoracic outlet syndrome
• recent surgery, pregnancy, estrogen-containing medicines and inherited clotting disorders

A clot in a vein just under the skin (superficial thrombophlebitis) causes a tender, cord-like red line, often at an old IV site.

Lymphedema, including after ALND

Lymphedema is swelling caused by lymph fluid that cannot drain away. In the arm, by far the most common cause is treatment for breast cancer: axillary lymph node dissection (ALND), in which many lymph nodes are removed from the armpit, and radiotherapy to the armpit. The risk is much lower after sentinel lymph node biopsy, where only one to a few nodes are removed.

Arm swelling after ALND can start within weeks or years later. Early signs include:

• a feeling of heaviness, fullness or tightness before any swelling is visible
• a sleeve or ring that feels tighter on the treated side
• swelling that is soft and pitting at first, then becomes firmer over time
• swelling that worsens with heat, air travel or heavy use of the arm

Report early signs promptly. Lymphedema treated early is easier to control. A sudden red, hot, swollen arm on the treated side is often cellulitis, which is more common in an arm with lymphedema and needs antibiotics the same day.

Other local causes

• Bursitis: fluid in the bursa at the tip of the elbow gives a soft, egg-shaped swelling (bursitis), often after leaning on the elbow.
• Insect bites and stings: large local reactions can swell the whole forearm for several days.
• Allergic reaction to a vaccine: a sore, swollen upper arm for 1 to 3 days is common.
• IV infiltration: fluid from a drip leaking into the tissues swells the hand and forearm, usually cool and pale.
• Tumors: rarely, a lump in the armpit or a mass pressing on veins or lymph vessels causes slowly increasing swelling.

Causes of swelling in both arms

When both arms swell, usually along with the legs, the problem tends to be fluid retention throughout the body:

• Heart failure: a weak heart lets fluid back up into the tissues. Leg and ankle swelling usually comes first. Arm swelling suggests significant fluid overload. Breathlessness on exertion or when lying flat and rapid weight gain are typical. Read more on heart failure.
• Kidney disease: damaged kidneys hold on to salt and water and may leak protein, causing puffiness around the eyes, hands and legs.
• Liver disease: low blood protein (albumin) lets fluid leak out of vessels.
• Underactive thyroid: can cause puffy, non-pitting swelling of the hands and face.
• Medicines: calcium channel blockers such as amlodipine, steroids, NSAIDs, some diabetes medicines and estrogen.
• Superior vena cava syndrome: a tumor or clot blocking the large vein that drains the head and arms causes swelling of the face, neck and both arms. This needs urgent care.
• Pregnancy: mild hand and finger swelling is common, but sudden swelling of the face and hands may be a sign of preeclampsia.

Arm swelling causes compared

Swollen arm and the heart

People often ask whether a swollen arm is a heart problem. A single swollen arm is rarely caused by the heart. Heart failure causes swelling where gravity pulls fluid, so it shows first in the ankles, legs and lower back. If your arm swells along with your legs and you are short of breath, see a doctor promptly.

Arm pain (not swelling) can be a heart warning sign. Pain spreading into the left or both arms with chest pressure, sweating or nausea can be a heart attack. Call 911 or your local emergency number.

Swelling on the right arm vs left arm

The side does not change the list of causes much. A few points help:

• The right side is more often affected by effort thrombosis because most people are right-handed.
• The left side is more often affected by pacemaker and some central-line clots, because devices are often placed on the left.
• The side of any breast or armpit surgery is the side at risk of lymphedema.

A knot on the arm with swelling

A localized lump with swelling around it is usually one of:

• a hematoma after a knock or blood draw (tender, bruised, shrinks over 1 to 3 weeks)
• an abscess or infected hair follicle (red, painful, may come to a head)
• a swollen lymph node in the armpit or above the elbow reacting to an infection in the hand
• a lipoma or cyst (soft, painless, slow-growing)

A lump that is hard, fixed, painless and growing, or larger than about 5 cm (2 in), should be checked to rule out a soft-tissue tumor. See arm lump or mass.

How doctors find the cause

Your doctor will ask when the swelling started, whether it is one or both arms, about recent injuries, IV lines, cancer treatment, exercise, travel and medicines, and about breathlessness or weight gain. They will compare the arms, check for pitting, warmth, redness and pulses, and examine the armpit and neck.

Common tests:

• Duplex ultrasound of the arm veins, the first test for a suspected clot
• Blood tests: complete blood count, kidney and liver function, albumin, thyroid tests and sometimes BNP for heart failure
• X-ray after an injury
• Echocardiogram if heart failure is suspected
• Limb volume measurement or bioimpedance to track lymphedema
• CT or MRI if a mass or a central vein blockage is suspected

Treatment and home care

Treatment targets the cause:

• Injury: rest, ice for 15 to 20 minutes at a time, compression with a light wrap, and raising the arm above heart level. Remove rings early.
• Cellulitis: antibiotics, with the edge of the redness marked so you can see if it spreads.
• Arm DVT: blood thinners, usually for at least 3 months. A catheter-related clot may mean removing the line.
• Lymphedema: complete decongestive therapy from a trained therapist (manual lymphatic drainage, multilayer bandaging, exercises, skin care), then fitted compression sleeves.
• Heart, kidney or liver causes: water pills (diuretics), salt restriction and treating the underlying disease.

At home, while you wait to be seen:

• Raise the arm on pillows so the hand is above the elbow and the elbow is above the heart.
• Gently open and close your fist and bend the elbow to help fluid move.
• Avoid tight sleeves, watches and rings.
• For pain, acetaminophen (paracetamol) or ibuprofen may help. Follow the label dose. Avoid NSAIDs if you have kidney disease, heart failure or stomach ulcers.

Frequently asked questions

Why is my arm swelling for no reason?

Swelling without an obvious injury is most often a minor sting, overuse or infection, but a blood clot, lymphedema or a body-wide problem such as kidney disease can also cause it. Swelling of a whole arm that appears over hours, especially with aching or a bluish color, should be checked the same day with an ultrasound.

How long after ALND can arm swelling start?

Lymphedema after axillary lymph node dissection most often appears in the first 2 to 3 years, but it can start months or many years later. Short-lived swelling in the first weeks after surgery is common and often settles. Report persistent heaviness, tightness or a change in sleeve fit.

Can a swollen arm be a sign of a heart problem?

Rarely by itself. Heart failure usually swells the ankles and legs first. Swelling of both arms with leg swelling and breathlessness can reflect fluid overload. Arm pain with chest pressure, sweating or nausea is a heart attack warning sign and needs emergency care.

What does a blood clot in the arm feel like?

It usually causes a dull ache or heaviness, swelling of the whole arm or forearm, warmth and a reddish or bluish tinge. Veins over the shoulder and chest may become more visible. Symptoms often follow a PICC line, pacemaker, or heavy overhead exercise.

How do I reduce swelling in my arm at home?

For minor swelling, raise the arm above heart level, use cold packs for 15 to 20 minutes at a time after an injury, move the fingers and elbow gently, and remove tight jewelry. If swelling is spreading, red, hot or unexplained, see a doctor rather than treating it at home.

Is swelling in the right arm more serious than the left?

No. The side alone does not make it more or less serious. What matters is how fast it came on, whether it is red and hot or bluish, and whether you have other symptoms such as fever or breathlessness.