A blister, also known as a vesicle or bulla, involves the build-up of fluid under the skin. This happens because of damage to that part of the skin. The most common cause of a ‘water blister’ is friction – for example, new shoes rubbing against the back of the heel.
Other common causes of blisters include burns (including sunburn). Blisters might appear with insect bites and contact dermatitis, too.
Blisters might also form in response to a viral infection, such as chickenpox or cold sores, or a bacterial infection, such as impetigo (a more serious cause of blisters), among other uncommon causes.
When to see your doctor
Your child should see a doctor if:
- the blister is filled with greenish fluid, or the surrounding skin is red or warm, because this might mean that the blister’s infected
- your child has multiple blisters and a fever, or isn’t well.
The fluid inside a blister is usually sterile, as long as the thin covering of skin over the blister hasn’t broken. So for an uncomplicated blister, you should avoid bursting it, because this can lead to infection.
If the blister bursts, apply a small pad of foam, with a hole cut in the centre, to prevent further pressure on the painful area. Dab with antiseptic solution twice a day, and keep the wound as clean as possible. It should dry up in a few days, and the skin will then peel.
If you’re dealing with a blister caused by shoes, it can help to have your child wear open shoes, or shoes that don’t press on the blisters.
Blisters caused by other things might need specific treatment, such as antibiotics for impetigo.
Make sure your child wears shoes that are neither too tight nor too loose. If your child has new shoes, put sticking plaster on the back of the heels for the first week, until she ‘breaks in’ the shoes.