What could cause swelling in only one hand?

September 25, 2025 •

4 min read

According to the National Health Service (NHS), swelling in the hands and arms is often caused by a buildup of fluid in these areas. When this swelling affects only one hand, the cause is typically localized to that specific limb, rather than being a systemic issue affecting the entire body. Understanding what could cause swelling in only one hand is the first step toward finding relief and determining if medical attention is necessary.

Quick Summary

Localized trauma, infections, and allergic reactions are common culprits for swelling in one hand. More serious but less frequent causes include blood clots, lymphedema, and certain rheumatological conditions that can affect one side of the body. A key aspect of identifying the root cause lies in considering recent activities, injuries, or other accompanying symptoms.

Key Points

Injury & Overuse: Trauma like a sprain or fracture, as well as repetitive stress from activities, are frequent causes of localized swelling.
Infections: A cut or wound can become infected, leading to localized swelling, redness, and pain, requiring prompt medical attention.
Blood Clot Risk: A deep vein thrombosis (DVT) in the arm can cause unilateral hand swelling and requires immediate medical evaluation.
Lymphedema: Chronic swelling in one hand can be a sign of a lymphatic system blockage, sometimes resulting from surgery or infection.
When to See a Doctor: Seek immediate care for severe pain, signs of infection like fever, or any associated shortness of breath.

Common Causes of Unilateral Hand Swelling

When swelling affects just one hand, the reason is often due to an issue that is confined to that specific limb. This can range from minor, temporary problems to more significant health concerns.

Injuries and Repetitive Stress

Trauma is a frequent cause of one-sided hand swelling. A fall, a heavy object dropped on the hand, or a sprain can lead to inflammation and fluid buildup as the body responds to the injury. Repetitive stress injuries, such as carpal tunnel syndrome or tendinitis, can also cause swelling, particularly in individuals who use their hands for repetitive tasks, such as typing or certain sports. For example, overuse of one hand with free weights or other weighted exercises can lead to swelling.

Infections

An infection, especially if it enters through a cut, bite, or puncture wound, can cause localized swelling. The body's immune system sends white blood cells to fight the infection, which can result in redness, pain, and swelling. Several types of hand infections can cause this, including:

Cellulitis: A common bacterial skin infection that can cause redness, swelling, and warmth.
Abscess: A deep, localized infection beneath the skin that results in a collection of pus.
Paronychia: An infection around the fingernail folds, which is particularly common in nail-biters.
Felon: A painful and tight infection in the fatty pulp of the fingertip, requiring urgent drainage.

Allergic Reactions

Contact dermatitis, an allergic skin reaction, can cause localized swelling and hives after exposure to a specific allergen. This could be from a new soap, lotion, or a plant. Additionally, an insect bite or sting on one hand can cause a localized allergic response, resulting in swelling that is limited to that area. In rare cases, angioedema, a deeper allergic reaction, can cause significant swelling.

Lymphedema

Lymphedema is a condition caused by a blockage in the lymphatic system, which can cause fluid to build up and result in swelling. If the blockage or damage is localized to one side, such as from surgery or radiation in the armpit area, it can cause swelling in only one arm and hand. Puffy hand syndrome, a condition sometimes associated with intravenous drug use, is another form of lymphedema.

Blood Clots

A blood clot in a vein in the arm, known as deep vein thrombosis (DVT), can cause swelling in the affected arm and hand. The clot blocks blood flow, causing a buildup of pressure and fluid. This can be a serious medical condition requiring immediate attention.

Less Common, But Serious Causes

While many causes are minor, some less common conditions can lead to unilateral hand swelling.

Rheumatological and Autoimmune Diseases

Certain inflammatory conditions can cause asymmetrical swelling. Psoriatic arthritis, for instance, is an inflammatory form of arthritis that can affect one hand or even a single finger. Other rheumatological diseases like rheumatoid arthritis and scleroderma can sometimes present asymmetrically.

Comparison of Common and Serious Causes


Cause	Onset	Associated Symptoms	Urgency	Treatment	Recovery
Injury/Trauma	Sudden, after incident	Pain, bruising, limited movement	Usually moderate, severe with fracture	R.I.C.E., pain management, physical therapy	Weeks, depending on severity
Infection	Gradual, but may be rapid	Redness, warmth, throbbing pain, pus	Moderate to high, can become systemic	Antibiotics, sometimes surgical drainage	Days to weeks
Allergic Reaction	Rapid, after exposure	Itching, hives, rash	Low to moderate, but high for angioedema	Antihistamines, corticosteroids	Hours to days
Blood Clot (DVT)	Can be sudden or gradual	Pain, redness, warmth, shortness of breath	High, requires immediate medical help	Blood thinners, medical supervision	Varies, can be long-term
Lymphedema	Gradual over time	Heaviness, skin changes, swelling unresponsive to elevation	Chronic, requires long-term management	Compression therapy, physical therapy	Ongoing

When to Seek Medical Attention

While minor swelling often resolves on its own, certain symptoms warrant a visit to a healthcare provider. You should seek immediate medical attention if the swelling is accompanied by:

Severe, sudden pain
Signs of infection, such as redness, warmth, and fever
Shortness of breath or chest pain, which could indicate a serious blood clot
Numbness or tingling
Swelling that does not improve after a few days of at-home care

Diagnostic Process and Treatments

Your doctor will likely start with a physical exam and a review of your medical history. They may ask about recent activities, past injuries, and the timeline of the swelling. Diagnostic tests, such as blood tests, X-rays, or ultrasounds, may be used to pinpoint the cause.

Treatment Options

For injuries: Rest, ice, compression, and elevation (R.I.C.E.) are often recommended for mild injuries. More severe injuries, like fractures, may require casts or surgery.
For infections: Antibiotics are prescribed for bacterial infections. Some infections, like abscesses, may need to be drained surgically.
For allergic reactions: Antihistamines and avoiding the allergen are the primary treatments.
For blood clots: Blood thinners are used to prevent the clot from growing and to allow the body to break it down naturally.
For lymphedema: Management often includes compression garments, massage, and exercises.

In all cases, proper diagnosis is crucial. For further information on the lymphatic system and lymphedema, you can consult the National Cancer Institute.

Conclusion

Swelling in one hand can be caused by a wide range of factors, from a minor injury or allergic reaction to more serious conditions like an infection or blood clot. It's important to pay attention to your body and recognize the accompanying symptoms. While many minor causes can be treated at home, any severe or persistent swelling, especially with other alarming symptoms, should prompt a visit to a healthcare professional for a proper diagnosis and treatment plan.

Frequently Asked Questions

You should be concerned about swelling in one hand if it is sudden, severe, or accompanied by symptoms like severe pain, fever, redness, warmth, or shortness of breath. These could indicate a serious issue such as an infection or blood clot, and you should seek immediate medical attention.

Yes, an insect bite or sting on one hand can cause a localized allergic reaction, leading to swelling that is confined to that hand. The swelling is typically accompanied by itching and redness.

While systemic issues with the heart or kidneys typically cause swelling in both hands, an issue can sometimes appear more prominent on one side. However, localized causes like injury or infection are more likely to cause unilateral swelling.

Puffy hand syndrome is a form of lymphedema, or fluid buildup, in the hands, often associated with long-term intravenous drug use. It is caused by progressive damage to the lymphatic vessels and can initially present as asymmetrical swelling.

For minor injuries, you can reduce swelling by elevating your hand above your heart, applying a cold compress, and using gentle compression. However, if the swelling is persistent or severe, or if you suspect an underlying condition, you should consult a doctor.

Yes, some forms of arthritis, such as psoriatic arthritis, can cause inflammation and swelling that affects one side of the body or even a single joint. Other types like rheumatoid arthritis can also sometimes present asymmetrically at first.

Unilateral hand swelling affects only one hand, suggesting a localized cause like an injury or infection. Bilateral hand swelling affects both hands and typically indicates a systemic problem, such as a heart, kidney, or liver condition.