Understanding Blisters - the Basics

What Are Blisters?

Most blisters are due to irritation or other damage to the skin from an external source, such as a shoe, although some can result from a disease or other ailment. A single blister is usually the result of friction or a minor burn, typically on the hands, feet, or other exposed areas.

What Causes Them?

Blisters are caused by several things:

Friction: Blisters can develop when a surface rubs against exposed skin, such as a tool handle against the hand or a new pair of shoes against the ankle. Unlike corns and calluses, which develop from prolonged rubbing, friction blisters come from brief, intense contact.

Burns: Flames, steam, or contact with a hot surface can cause blisters, as can severe sunburn or exposure to other types of radiation.

Contact with irritants: Skin may blister when it comes in contact with chemical irritants, cosmetics, and many plant and animal toxins. This is called contact dermatitis.

Drug reactions: Many people develop blisters as a reaction to taking certain oral and topical drugs. Before prescribing any new drugs, a doctor should ask you about any drug reactions you may have had in the past. If you develop a blister while on medications, you should call your doctor.

Autoimmune diseases: Of the various autoimmune diseases known to cause blistering, three are most common. Pemphigus vulgaris, a potentially fatal skin disorder, causes blisters in the mouth that sometimes spread to the head and other parts of the body; the painful blisters become raw and crusted before bursting. Bullous pemphigoid causes less severe eruptions that heal faster and are not life-threatening; this condition is seen chiefly in the elderly. Dermatitis herpetiformis causes small, itchy blisters; it is a chronic condition that usually starts in early adulthood.

Infection: Blisters are a common symptom of many infectious illnesses, including chickenpox, cold sores, shingles, a skin infection called impetigo, and fungus infections such as ringworm.