Foot blisters are caused by repetitive friction, burns, cold injuries, forceful pinching of the skin and spider bites, according to WebMD. Viral infections such as chicken pox, cold sores and shingles, and bacterial infections such as impetigo can also cause blisters on the foot and other parts of the body.
Some other foot blister causes are reactions to medication, skin contact with allergens or irritants and certain autoimmune diseases, states WebMD. If the blisters occur with other symptoms, such as fever or chills, it could point to a more serious illness, and medical attention is suggested.
If a blister isn't painful, it's best to cover it with a bandage and allow it to heal, according to Mayo Clinic. The skin covering the blister is a layer of protection against bacteria, and leaving it intact helps prevent infections. It is recommended to seek medical attention if the pressure of the foot blister is painful or affecting the ability to walk.
Draining a blister is not recommended, especially in patients with other symptoms, warns WebMD. If a blister does open,it is recommended to wash the area with water, apply antibiotic ointment and protect the wound with a bandage. Change the bandage daily or whenever it gets dirty until the wound heals.