Blisters

What are blisters?

A blister is formed when fluid from blood vessels leaks into the skin. It then collects beneath the outer layer of skin, forming a raised bump.

As new skin grows beneath the blister, the fluid contained within it is slowly absorbed, and the skin on top dries and peels off. Hence the blister heals naturally and rarely needs treatment.

Causes and risk factors

Single blisters are usually caused by friction when something rubs against the skin. Poorly fitting shoes are a common example of this. Any kind of burn - including sunburn - can cause blisters, too.

Certain medical complaints cause blisters to appear on different parts of the body. These include eczema, chickenpox and the bacterial infection impetigo, where the blisters may be filled with pus rather than the usual clear fluids.

Blisters can also form as a reaction to certain medications, including some antibiotics, and there are a number of rarer blistering skin conditions, some of which are caused by an autoimmune reaction, where the body's immune system attacks cells in the skin.

Treatment and recovery

Never burst the blister to release the fluid because the skin acts as a barrier against infection. When the skin of the blister breaks of its own accord or as a result of minor trauma, a sterile dry dressing should be used to cover it, which protects the area from infection until it's healed.

If the blister becomes red, hot, filled with pus, or painful then medical advice should be sought, because treatment for possible infection may be needed. Recurrent blisters, blisters in a wide-spread rash unrelated to friction, or blisters accompanied by other unusual symptoms should all be checked by a doctor because they may a sign of a more complex condition that needs investigation.