What causes skin blisters?

Shoes, tools, or repeated rubbing can create a local friction blister. Heat, chemical exposure, sunburn, or cold injury can damage the outer skin and cause fluid to collect. Contact dermatitis may produce itchy blisters after an irritating or allergic exposure, while dyshidrotic eczema often causes tiny, intensely itchy blisters on the palms or sides of the fingers and feet. Cold sores, chickenpox, and shingles are viral causes with characteristic grouped or widespread patterns. Blisters can also occur in less common immune-related skin disorders, so appearance and timing matter.

Wash gently, pat dry, and cover a blister with a clean non-stick dressing. Reduce rubbing and avoid deliberately popping it; the surface helps protect the raw skin beneath. If it breaks, rinse with clean water and replace the dressing. Do not apply strong household chemicals or unprescribed creams. A clinician may consider antiviral treatment when a viral pattern is suspected.

Get medical help for blisters over a large area, severe burns, rapidly spreading lesions, marked pain, pus, increasing warmth, fever, or blisters affecting the eyes, mouth, or genitals. Seek prompt care if new blisters follow a medicine or are accompanied by skin peeling, breathing trouble, or facial swelling. People with diabetes or reduced immunity should arrange advice early.

Does the distribution suggest friction, infection, dermatitis, or another cause? Should the blister be tested or drained? Which dressing is suitable, and what symptoms would indicate infection or a medicine reaction?