Blisters

Overview

A blister is a small pocket of clear fluid that forms between the upper layers of the skin. It is the body's way of cushioning and protecting damaged skin underneath. Most blisters are caused by friction or minor burns and heal on their own within a few days to a couple of weeks.

Blisters can also signal an infection, a burn, an allergic reaction, or an underlying skin condition. The fluid inside is usually clear but may be cloudy if infected or bloody if a small blood vessel was damaged. Knowing the likely cause helps you care for a blister safely and recognize the less common situations that need medical attention, such as widespread, recurrent, or unexplained blistering.

The location and pattern of blisters often hint at the cause. Friction blisters tend to form on the hands and feet where rubbing is greatest, while a band of painful blisters on one side of the body suggests shingles. Blisters in the mouth, around several areas at once, or appearing without any obvious injury are more likely to reflect an infection, an allergic reaction, or a skin disease, and these deserve closer evaluation.

Common Causes

Blisters form when the skin is damaged and fluid collects to protect the area. Common causes include:

• Friction: Repeated rubbing from shoes or tools, especially on hands and feet.
• Burns and scalds: Heat, sunburn, steam, or chemicals.
• Infections: Viral infections such as chickenpox, shingles, and cold sores, and bacterial infections such as impetigo.
• Allergic and contact reactions: Contact dermatitis from plants, metals, or chemicals.
• Frostbite: Damage from extreme cold.
• Skin conditions: Eczema and rarer blistering disorders.

Associated Symptoms

The symptoms around a blister help identify the cause and any complications:

• Pain or tenderness, common with friction and burn blisters
• Itching, often with eczema or allergic reactions
• Redness, warmth, increasing pain, or pus, suggesting infection
• Fever or feeling unwell, which can accompany infections like chickenpox or shingles
• A band of blisters on one side of the body, typical of shingles

Widespread blistering, blisters in the mouth or eyes, or skin that peels in sheets can indicate a serious reaction and needs urgent care.

Diagnosis & Evaluation

Most blisters are diagnosed by their appearance and the story of how they developed. A clinician will ask about friction, burns, new products, illnesses, or medications.

• Visual exam: Looking at the size, distribution, and contents of the blisters.
• Swabs or cultures: To identify a viral or bacterial infection.
• Skin biopsy: For unexplained or recurrent blistering to check for an autoimmune skin disorder.
• Patch testing: When an allergic contact cause is suspected.

Treatment & Management

Care depends on the cause, but most friction and minor burn blisters heal best when left intact.

• Leave it covered: Protect the blister with a clean, soft dressing and avoid popping it, since intact skin guards against infection.
• If it bursts: Gently clean the area, keep the loose skin if possible, apply an antibiotic ointment if advised, and cover it.
• Burns: Cool the area under running water and cover; seek care for large or deep burns.
• Infections: Antiviral medicines for shingles or cold sores, and antibiotics for bacterial infections such as impetigo.
• Allergic and eczema blisters: Avoid triggers and use soothing or steroid creams as advised.

Self-Care & Prevention

• Wear well-fitting shoes and use socks, gloves, or padding to reduce friction
• Apply blister plasters or tape to hot spots before they blister
• Use sunscreen and protective clothing to prevent sunburn
• Handle hot liquids and chemicals carefully
• Keep eczema and other skin conditions well controlled

When to See a Doctor

See a doctor if a blister shows signs of infection — spreading redness, warmth, increasing pain, pus, or fever — or if you have blisters with no clear cause. Seek emergency care for:

• Widespread blistering or skin peeling off in sheets
• Blisters in the mouth, eyes, or genitals as part of a severe reaction
• A large or deep burn, an electrical burn, or a chemical burn
• Blisters after starting a new medication along with fever or feeling very unwell

A severe blistering drug reaction is a medical emergency — seek immediate care.

Related Topics

Frequently Asked Questions

References

1. MedlinePlus, U.S. National Library of Medicine. Blisters.
2. American Academy of Dermatology Association. How to treat blisters.
3. Mayo Clinic. Blisters: First aid.
4. National Health Service (NHS). Blisters.