If tests don’t suggest a cure, simple changes to diet, or perhaps reviewing medication, may be the answer says Dr Mel Wynne-Jones

Lady talking to doctor

Cold sores and chickenpox are both types of blister © iStock

We all get blisters from time to time, usually on our feet or hands; our skin reacts to friction, pressure, burns or scalds by producing a painful swelling filled with clear fluid (or occasionally blood) that helps to protect against further damage (see tips box for how to cope).

Those caused by sunburn and photodermatoses (sensitivity to sunlight) are best avoided by using sunblock and staying in the shade.

But blisters that appear for no obvious reason may need blood tests and/or skin biopsy (samples) to identify them.

Cold sores and impetigo

These both produce one or more painful blisters that weep and crust, usually around the mouth, but occasionally elsewhere on the face or body.

The fluid they contain can transfer infection to other areas and people, so good hygiene is essential.

Cold sores are caused by the herpes simplex type 1 virus, and you may notice tingling or burning beforehand. Treat immediately with antiviral cream or other pharmacy treatments.

Your GP may prescribe antiviral tablets for severe or recurrent cold sores. Impetigo blisters produce yellowy crusts. They are caused by streptococcal/staphylococcal bacteria and often need antibiotic tablets.

Eczema and dermatitis

Eczema (Greek for ‘to boil’)is common and can produce tiny weeping blisters, as well as widespread dryness and itching.

Dermatitis looks similar, but is an allergic reaction, for example, to nickel or household chemicals.

They’re both treated with emollients (medical moisturisers) and steroid creams or ointments, plus antibiotics if skin becomes red and infected.

Chickenpox and shingles

Children who get chickenpox, caused by the zoster virus, may be off-colour, feverish and infectious before the crops of blisters appear.

These are infectious until they crust over, although scabs take longer to drop off.

Paracetamol and/or antihistamines can relieve fever, discomfort and itching. Adults, pregnant women and people with poor immunity are more likely to feel very ill.

They need antiviral treatment, usually in hospital, and may develop serious complications such as pneumonia and inflammation of the brain.

Zoster virus can then ‘hide’ in the nervous system, reappearing years later as shingles – a painful patch of blisters on one side of the body or face. Early treatment with antiviral tablets will help.

Post-shingles pain (neuralgia) can persist and is treated with drugs, such as amitriptyline, that block pain signals.

Scalded skin

SSSS (staphylococcal scalded skin syndrome) produces fever and large, extensive blisters requiring hospital treatment.

Stevens-Johnson syndrome is a rare allergic reaction to antibiotics that can produce severe blistering of the lips and mouth and a widespread red rash.

Epidermolysis bullosa is a genetic disorder that makes skin and internal membranes fragile and prone to blisters, usually from childhood.

Pemphigus and pemphigoid are immune disorders that produce widespread blisters affecting the mouth and body that may scar.

They can be triggered by drugs, stress, hormones, pregnancy, burns, tumours and other environmental factors.

You’ll need treatment with steroids or stronger immune-system drugs.

6 ways to cope with blisters

1 Think prevention! Avoid tight shoes, wear gloves for DIY/gardening or use a rub-on anti-blister stick to reduce friction.

2 Don’t pop blisters as this could allow infection to enter. If a blister bursts naturally, cover it with a clean dressing until it heals (for up to a week).

3 Use a hydrocolloid dressing (from the pharmacy) to act as a cushion and speed up fluid reabsorption.

4 Ask about antibiotics if you see signs of infection (yellow pus, increasing redness or pain).

5 Run cold water over a scald for 10 minutes. Go to A&E, unless it’s very small.

6 See your GP if blisters are multiple and have no obvious trigger.