A blister is a small pocket of fluid in the upper skin layers and is a common response to injury or friction. The feet are particularly prone to blisters. Blisters rarely need medical attention unless they are severe, recurrent, caused by burns or are due to an underlying infection. Multiple blisters that develop spontaneously, especially in older people, may indicate an auto-immune condition and require referral to a specialist dermatologist.
1. What is blister?
A blister is a small pocket of fluid in the upper skin layers and is one of the body's responses to injury or pressure. The feet are particularly prone to blisters. Ill-fitting shoes or friction can damage the skin, and a blister forms to cushion the area from further damage as it heals. If the blister is left unpopped, the body gradually absorbs the fluid as the underlying skin recovers. This can take around one week.
Depending on the cause and location, a blister can range from the size of a pinprick to three centimetres or more in diameter. A blood blister is usually caused by a severe pinch or bruise to the skin that breaks the tiny blood vessels (capillaries).
2. Symptoms of a blister
Blister symptoms include:
a reddened and tender patch of skin
a raised lump filled with clear fluid or, sometimes, blood.
3. Causes of blisters
Some common causes of blisters include:
- ill-fitting shoes
- friction (for example, using a shovel all day without gloves can cause blisters on the palms of the hands)
- scalds or burns
- severe sunburn
- allergic reaction to irritants
- viral skin infection (such as herpes or warts)
- fungal skin infection (such as tinea on the soles of the feet or between the toes).
4. Self-help for blisters
Blisters rarely need medical attention, unless they are severe, recurrent, caused by burns or are due to an underlying infection.
When treating a blister, if possible, resist the temptation to burst it. You could cause an infection or hinder your body's healing process. If this is not possible, the best way to burst a blister is to clean the area with soap or disinfectant and then prick the blister with a needle heated over a flame to sterilise it.
Allow the fluid to slowly escape and the roof of the blister to collapse down onto the blister base. The roof then acts as a dressing that can be further covered with a dressing or sticking plaster. Do not remove the blister roof, as that will delay healing and increase the risk of infection. If the blister refills over the next day or so, you can repeat the process.
Other suggestions for treating a simple friction blister include:
If the blister has burst, don't peel off the baggy skin pocket – let your body heal the area in its own way and in its own time.
Apply antiseptic and a dressing or sticking plaster to the area to protect it and keep it free from dirt or irritants.
Don't use tape alone for the dressing, as removing the tape may rip the roof skin off the blister.
Change the dressing daily and re-apply antiseptic.
Avoid 'folk remedies' like applying butter or vinegar. These don't work.
5. When to seek medical attention for a blister
See your doctor or other health professional for treatment if:
- the blister is caused by a burn, scald or severe sunburn
- the blister starts weeping pus (yellow or green, sometimes smelly, fluid)
- the area becomes increasingly swollen or inflamed
- you suspect the blister is infected
- you develop multiple blisters without any preceding skin injury.
6. Prevention of blisters
Blister prevention strategies include:
- Wear properly fitted shoes.
- Choose moisture-wicking socks (socks that draw sweat away from your feet) or change socks twice daily if you have sweaty feet, as wet socks cause friction and rubbing.
- Wear 'sports socks' when exercising or playing sports.
- If you become aware of a localised 'hot' area on your foot, stop your sport and tape the area immediately.
- Apply a foot spray deodorant to reduce sweating and the risk of fungal infection.
- Change damp socks promptly, as wet socks can drag against the skin.
- Wear heavy-duty work gloves when using tools such as shovels or picks.
- Protect yourself against sunburn with clothing, hats and sunscreen lotions.
- Avoid unnecessary skin contact with chemicals.
- Be careful when dealing with steam, flames or objects that radiate heat (such as electric stovetops).