A blister is raised skin filled with clear fluid. Pressure, heat, moisture, friction or burns can cause a blister to form on the skin. For example, a blister may form on your heel when it rubs against the inside of a shoe. Or a blister may form on your thumb after you hold a kayak paddle.

Blisters are usually minor injuries that you can treat yourself.

If a blister isn't too painful, try to keep it from breaking open. Unbroken skin over a blister may provide a natural barrier to bacteria, and it decreases the risk of infection. Cover the blister with a bandage or moleskin. Moleskin is a durable fabric that can help protect blisters in high-friction areas.

Cut a piece of moleskin about 1 inch (2.5 centimeters) larger than your blister. Fold the nonsticky sides together and cut a half-circle that's about the size of your blister. When you unfold the moleskin, you have a hole in the middle that's about the size of your blister. Apply the moleskin over the blister, aligning your blister with the hole you made. Then cover the blister and moleskin with gauze.

To relieve blister-related pain, drain the fluid while leaving the skin above the blister in place. If you have diabetes or poor circulation, or tend to get infections, take extra care to prevent infection.

How to drain a blister and help prevent infection:

1. Wash your hands and the blister with soap and water.
2. Apply an antiseptic to the blister.
3. Clean a sharp needle with an antiseptic wipe or rubbing alcohol.
4. Use the needle to prick the blister in several spots near the edge. Let the fluid drain but leave the skin above the blister in place.
5. Apply an antibiotic ointment or petroleum jelly to the blister and cover it with a nonstick bandage or gauze pad.
6. After several days, cut away the dead skin. Use tweezers and scissors that you sterilize with an antiseptic wipe or rubbing alcohol. Apply more ointment and a bandage.
7. Check the area every day for infection.

Seek medical care if the blister looks infected. Signs of infection include expanding skin color changes that spread out from the blister, increasing pain, pus or warm skin.

These tips can help prevent blisters:

• Wear shoes that fit well. Try the various shoes and insoles that are designed to help reduce blistering.
• Choose socks made with moisture-wicking fabric. Avoid cotton socks. Dust the inside of your socks with foot powder.
• Before your activity, tape spots that tend to get blisters. Athletic tape and duct tape work well for this.
• Place moleskin or gel-filled blister bandages inside your shoes for extra padding.
• Select gloves suited for your activity.
• If you develop a hot spot, that's a sign that a blister is forming. Treat it right away by applying tape, a blister bandage or moleskin.
• Change into dry socks as needed, as moisture increases the risk of blisters forming.