Blisters

Blisters are small, fluid-filled pockets that form between the layers of the skin, most often as a result of friction but also from burns, chemical exposure, infections, or certain medical conditions. The fluid is usually clear and called serum, but blisters may contain blood (hemorrhagic bullae) or pus if infection is present. They are most common on areas subjected to repeated rubbing, such as the hands, feet, heels, or toes.

The underlying mechanism involves separation of skin layers, allowing fluid to collect and cushion the damaged tissue. Friction blisters develop with repetitive rubbing; burn blisters arise after thermal injury; chemical blisters follow exposure to caustic substances. Risk factors include ill-fitting footwear, prolonged activity, humidity, diabetes, and vascular disease.

Symptoms commonly include a raised, tense area of skin that is tender to touch and filled with clear fluid. Large blisters (bullae) can be painful. If infection occurs, the skin around the blister may be red, warm, and may produce pus, sometimes with fever or spreading redness.

Management emphasizes preserving the blister when possible. Keep the area clean, protect with a sterile, nonadhesive dressing, and avoid popping the blister to reduce infection risk. If a blister is large or painful, it may be carefully drained with a sterilized needle after cleaning, followed by applying antibiotic ointment and a sterile bandage. Treat burns and chemical exposures with appropriate cooling and rinsing, and seek medical care for signs of infection, extensive burns, or blisters in at-risk individuals (such as those with diabetes).

Prevention focuses on reducing friction: proper footwear, moisture control, protective padding, and gradual increases in activity. Blisters usually heal without scarring once the skin re-epithelializes.