Dark or Black Blisters on the Skin

Blood trapped beneath the blister roof can look red, purple, brown, or nearly black. Other dark lesions may only resemble blisters, so the history and examination matter.

A pressure point, pinching injury, burn, or repeated rubbing can damage small blood vessels beneath the skin and create a blood blister. Contact dermatitis commonly presents with itchy blisters after exposure to a trigger, while shingles commonly presents with painful grouped blisters in a band on one side of the body.

Location provides useful context. Blisters between fingers or on palms and soles have a different pattern from those following a stripe around the torso. A dark centre with surrounding redness, increasing tenderness, or tissue breakdown is not typical simple friction damage.

Leave the blister roof intact when possible, wash gently, cover it with a clean non-stick dressing, and remove the source of friction or heat. Do not deliberately puncture it or peel away dark skin. If it opens, let fluid drain without squeezing, preserve the remaining roof, and replace a wet or dirty dressing.

Avoid sharing towels and close skin contact when several new blisters appear with fever or when shingles or chickenpox is possible. Antiviral medicines only help selected viral conditions and require clinical guidance.

Seek emergency assessment for rapidly spreading black or purple skin, severe pain that seems greater than the visible injury, confusion, faintness, breathing difficulty, or blistering involving the eyes, mouth, or genitals. Prompt review is also warranted for fever, pus, spreading warmth or redness, an unexplained cluster, or a blister in someone with diabetes, poor circulation, or reduced immunity.

Ask whether the blister appears traumatic, inflammatory, infectious, or related to a medicine; whether it should remain covered; and whether testing is needed. Report new prescriptions, recent burns or friction, pain before the rash, and contact with anyone who has a blistering illness.