What is a blister
A blister is a fluid filled sac that forms when the epidermis (the top layer of skin) has been damaged enough to separate it from the layers beneath causing a space. This space fills with fluid and the epidermis is pushed out as the fluid increases. The fluid protects the area from further damage.
The fluid in the blister sac is serum, a clear watery fluid. It is the part of the blood that is left if all the red blood cells and clotting agents have been removed.
Blisters are sometimes darker in colour if they are filled with blood (blood blisters). This normally happens if the skin is pinched or crushed and a small blood vessel near the surface ruptures allowing blood to leak into the area. If the area has been pinched or crushed then use an ice pack over the area (frozen peas from the freezer or an ice cube wrapped in a tea towel) for 10 minutes to minimise bleeding and trauma to the area.
You generally don't need to see your GP with a blister however blisters can sometimes become infected and you might need antibiotics. If it is infected, it may be yellow or green in colour and filled with pus rather then serum. If the blister is hot and painful and you have red streaks leading away from the blister you should see your GP as it is a sign that the infection is spreading.
You should also see your GP if you develop blisters and there has been no obvious cause i.e. there has been no rubbing, friction or injury to the area.
What can cause blisters
- Friction or rubbing from tight shoes
- Wearing shoes without socks
- Wearing shoes that you know cause you a problem
- Contact with some chemicals
- Excessive heat – from sunburn or if the area is scalded
- Wear comfortable well fitting shoes and socks
- Control sweat on your feet - blisters are more likely to occur on moist skin
- If your socks get wet or sweaty then change them regularly
- When playing sport wear moisture absorbing sports socks
- Wear appropriate shoes for your activity
- Apply foot cream
- If your feet get hot use a foot spray to cool them
Treatment for Blisters
It is preferable not to burst the blister as it provides a natural barrier to infection.
Most blisters heal naturally. Over the next 3-7 days new skin grows underneath the blister and the fluid is gradually re-absorbed. The outer layer will eventually dry and peel off.
If it is a very small blister which is not painful it might not need a plaster but if the area is uncomfortable or it is a larger blister, then cover up the blister with a plaster. I recommend special sterile hydrocolloid plasters as they will cushion the area and help make the blister more comfortable. Leave this type of dressing in place undisturbed for 3-7 days.
If the blister does burst, allow the fluid inside to drain away but leave the skin on top of the blister and cover with a sterile dressing. It is very important to cover the area to protect it from infection until it heals.
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