You use your thumbs throughout the day for holding, grasping, and opening objects, typing on your computer or smartphone, flipping through channels on your TV, and more.

You’re likely to notice when something goes wrong with your thumbs when doing everyday tasks becomes more complicated.

One common issue is swelling, or enlargement. Parts of the body usually swell up when fluid begins to collect inside them due to injury or illness.

There are several possible reasons why your thumb might swell up. Some are easily treatable at home, while others are more serious and require medical treatment.

The thumb is made up of three short bones connected by three joints. One joint is located just above your wrist bone, and the other two are located about halfway up your thumb and near the tip of your thumb.

There are different reasons why one or more of your thumb joints might be swollen.

Arthritis

Thumb arthritis is common as we age. In most cases, it’s osteoarthritis — the age-related breakdown of joint tissue — that causes a swollen thumb joint, especially at the lowest joint (called the basal joint).

It can also be caused by reactive arthritis, which is triggered by an infection in the body.

Symptoms of arthritis in the thumb include swelling, pain, and stiffness at the basal (lower) thumb joint.

Autoimmune diseases

Your body’s immune system is designed to fight foreign invaders like viruses and bacteria so you stay healthy.

Autoimmune diseases trick your body’s immune system into attacking itself instead. A few of these diseases may cause swelling in your thumb joints. They include:

Symptoms of autoimmune diseases vary, but some common ones include:

  • fatigue
  • sore muscles
  • swelling
  • redness
  • low fever
  • difficulty concentrating
  • numbness and tingling in the hands and feet
  • skin rashes
  • hair loss

Bone cancer

Bone cancer will affect about 3,500 new people in 2019, according to the American Cancer Society. Often, bone cancer occurs secondarily to other types of cancers that may affect the body — especially breast, lung, kidney, thyroid, and prostate cancer.

The thumb and middle finger are most commonly affected by secondary bone cancer. Signs of bone cancer in the thumb include:

  • swelling that continues to enlarge over time
  • redness
  • pain
  • loss of mobility
  • cancer in another part of the body

Dactylitis

Dactylitis is a secondary condition most commonly caused by psoriatic and rheumatoid arthritis. In some cases, it may also be caused by reactive arthritis.

Dactylitis causes your thumbs, and usually other fingers or toes, to swell so much that they look like small sausages. You may also experience pain and fever.

De Quervain’s tenosynovitis

De Quervain’s tenosynovitis is a condition that can cause pain and swelling at your wrist where your thumb attaches to your forearm. It’s caused by chronic overuse of the wrist, often by repetitive movements such as lifting a child into a car seat, carrying groceries, or playing golf or racket sports.

Symptoms include:

  • pain and swelling near the base of your thumb
  • difficulty moving your thumb and wrist when you’re holding or pinching something
  • a sticking sensation in your thumb when you move it

Fractured finger

A fracture can result from impact or trauma hard enough to break the bones in your thumb. A fracture can affect any part of the thumb, including the base. Symptoms include:

  • swelling
  • bruising
  • pain
  • warmth
  • limited range of motion

Gout

Gout is caused by a buildup of uric acid in the body. When gout flares up, it causes joint pain, swelling, and warmth. If you don’t seek treatment, you could develop permanent lumps in your joints, skin, and body tissues.

Sprained or jammed thumb

Sprains, or overstretching or tearing of ligaments, can affect your thumbs. It’s common in athletes, but anyone may experience a sprain when their thumb becomes hyperextended at one or more of its joints.

Symptoms of a thumb sprain include:

  • swelling
  • pain
  • redness or bruising
  • dislocation
  • lack of mobility

A jammed thumb can result from an impact to the tip of your thumb that pushes it back into your hand at the joint.

A jammed thumb may swell at any joint, but is likely to be especially swollen at the joint connecting it to the hand.

As with sprains in general, other symptoms include pain, lack of mobility, and redness.

Infection

It’s possible to develop an infection in your thumb joint that causes swelling. Causes for infection include an animal bite or scratch, or antibiotic-resistant bacteria getting into a wound.

Symptoms of infection include:

  • swelling
  • redness
  • fever
  • pain
  • pus coming from a wound on your thumb

Pregnancy

In pregnancy, the body produces extra blood and fluid to support a developing baby. This extra fluid commonly causes swelling, especially in the hands, face, legs, ankles, and feet.

Swelling is especially common in the fifth month, and can increase during your third trimester.

Medical emergency

If you notice sudden swelling in your hands and face, you could be experiencing preeclampsia, a condition causing high blood pressure and protein in your urine. See a doctor right away if you have these symptoms.

Trigger finger

Trigger finger is a type of thumb overuse injury that causes stiffness and swelling at the base of the thumb where it connects to the palm of your hand.

Other symptoms include soreness, tenderness, and a clicking or snapping noise when you move or try to bend your finger.

Some conditions affecting the base of the thumb can also affect one or both of the knuckles on your thumb, including:

  • arthritis
  • autoimmune diseases
  • bone cancer
  • dactylitis
  • gout
  • injury such as a fracture, sprain, or jammed thumb
  • infection
  • pregnancy
  • trigger finger

Other causes of swelling of the thumb at the knuckles include:

Bruised knuckle

Bruised knuckles are often caused by a hard injury from a fall, fistfight, auto collision, or athletics. These injuries cause the knuckle to swell and bleed under the skin, even if no bones are broken.

If you have a bruised knuckle, you’ll notice:

  • immediate pain on the knuckle and sides of the affected finger
  • discoloration
  • bleeding
  • swelling
  • tenderness
  • lack of mobility
  • popping sounds
  • inability to make a fist

In severe cases, you may experience hand numbness and weakness.

Tendonitis

Tendonitis, swelling caused by overuse of the hand’s tendons, is common. You may notice swelling at the knuckles in your thumb, and pain and stiffness when you try to bend them.

Flare-ups of tendonitis symptoms may appear when you engage in repetitive movements of your thumbs, such as when picking up heavy objects or using a cellphone.

Swelling between the thumb and index finger is less common than swelling affecting the joints. However, when swelling does occur, it’s most likely caused by De Quervain’s tenosynovitis.

Other conditions causing swelling in this area include:

  • autoimmune disease
  • bone cancer
  • dactylitis
  • gout
  • infection
  • jammed finger
  • pregnancy

Treatment for thumb swelling depends on its cause. Some causes are benign and can be treated at home. Others are more serious and require prompt medical treatment.

Home remedies

  • Apply heat and cold to help alleviate swelling caused by mild thumb injuries and arthritis.
  • Change your diet. Pregnant women may experience less swelling if they eat less salt, and people with gout can ease swelling by avoiding food containing purines. For those with autoimmune illnesses, eating anti-inflammatory foods may reduce swelling.
  • Soak your thumb in a warm or cool Epsom salt bath for 15 to 20 minutes.
  • Rest your thumb if you have a mild injury.
  • Apply a mixture of tea tree oil and carrier oil to the skin to reduce swelling and prevent mild infections.
  • Wash your hands regularly with soap and water to help prevent bacteria from entering wounds and causing infection.
  • Lose excess weight to ease pressure on your joints if you have chronic arthritis.
  • Yoga, exercise, and tai chi can help keep swollen joints more mobile and reduce overall swelling in people with arthritis, according to researchers.

Medical treatments

  • Antibiotics (oral and topical) may be needed to treat infections in the thumb.
  • Antirheumatic drugs and other arthritis drugs like corticosteroids can help reduce swelling in the thumb and other joints.
  • Chemotherapy or radiation may be needed to treat cancer in the thumb and other parts of the body.
  • Over-the-counter (OTC) nonsteroidal anti-inflammatory medications can reduce pain and swelling caused by mild injuries and chronic arthritis.
  • Immobilization, by holding a broken or injured thumb in place with a splint that is taped to your index finger, can keep your thumb rested so it can heal.
  • Steroids are sometimes used to treat autoimmune disorders and gout by reducing swelling.
  • Surgery is sometimes needed to remove cancerous growths in the thumb and to correct trigger finger, thumb fracture, and other injuries.

It’s possible to treat many causes of a swollen thumb at home with a short recovery time. However, more serious causes may require medical treatment. You should schedule an appointment with a doctor if your swollen thumb:

  • lasts more than 3 days or happens more than 3 times every month
  • was caused by trauma or serious injury, such as a fracture
  • is very painful
  • isn’t resolved with home remedies
  • was bitten by an animal or there is a wound on your hand that is leaking pus

Additionally, go to the doctor immediately if you are pregnant and your hands or face suddenly becomes swollen.

There are many possible causes of a swollen thumb. Many shouldn’t be concerning, while others are more serious.

How you treat your swollen thumb depends on its cause. When in doubt, schedule an appointment to see a doctor, especially if the swelling is accompanied by pain, redness, and fever.