•  Sore bump on the skin that may be filled with fluid. Swelling.

•  Pain and tenderness to the touch.

•  Friction on the skin. This is the main cause.

•  Skin rashes, frostbite, and second-degree burns.

•  Herpes simplex viruses.

•  Allergic reaction to medicine.

•  Epidermolysis bullosa (EB). This is a group of blistering skin conditions. With these, the skin is so fragile, even minor rubbing can cause blisters. Blisters can occur inside the body, too.

•  Wear shoes and socks that fit well. Wear moleskin pads on areas where socks or shoes rub the skin.

•  Apply an antiperspirant to the bottom of your feet before an athletic activity.

•  Wear gloves for activities that put friction on the hands, such as raking leaves.

•  Protect a blister from more friction. Cover it with a loose bandage or a moleskin pad. The skin over the blister protects it from infection.

•  If the blister is very painful, drain it. Clean the area with alcohol. Sterilize a needle. Gently, pierce an edge of the blister. Let it drain. If no dirt or pus is under the skin flap, pat it down to protect the skin below it. Wash the area well with soap and water. Apply an antibiotic ointment and cover it with a bandage or gauze and tape. Change this daily. Change it more often if it gets dirty or wet.