Blisters

A blister is a bubble of fluid under the skin, usually from friction, burns, or infection. Most are minor and heal on their own if left alone.

Common causes

• Friction — ill-fitting shoes, new walking/running shoes, long hikes, repeated manual work.
• Burns and scalds — heat, hot oil, hot tea/chai, hot steam (very common cooking injury). See Burns.
• Sunburn — blisters after prolonged unprotected sun.
• Contact dermatitis — plants, chemicals, nickel, henna-plus-PPD hair dye.
• Infections — chickenpox, shingles, cold sores, impetigo, hand-foot-mouth disease.
• Friction blisters in diabetes or neuropathy — may be painless and hide serious tissue damage.

What to do

• Leave it intact. The roof of the blister is the best natural dressing.
• If it's large, painful, or likely to break on its own, wash hands, clean a needle with alcohol flame, pierce at the edge, let the fluid out, keep the skin roof on, cover with a clean dressing.
• Don't apply turmeric, toothpaste, oil, kerosene, or ash — these cause infection.
• Change dressings if wet or dirty.
• For friction blisters, switch footwear; well-fitted cotton socks and gradual break-in prevent recurrence.

See a doctor

• Pus, spreading redness, warmth, fever — infected.
• Large blisters from burns or scalds — see Burns; anything bigger than a 5-rupee coin, on face, hands, feet, genitals, or a child needs medical review.
• Blisters in a person with diabetes — don't self-treat.
• Widespread or clustered blisters with fever — viral rash (chickenpox, shingles, HFMD).
• Painful clustered blisters along a strip of skin — shingles; an antiviral within 72 hours reduces long-term nerve pain.
• Large blisters with mouth/eye sores after a new drug — possible Stevens–Johnson syndrome, emergency.