Understanding Blood Blisters: What They Are, What to Do, and When to Get Help

A blood blister is a tender, dark spot under the skin filled with blood. It happens when small blood vessels break but the skin stays closed, trapping the blood inside. These blisters look red, purple, or almost black, and they usually show up after something pinches or rubs the skin hard—like a door closing on a finger or tight shoes rubbing the foot.

What causes a blood blister?
Most often, blood blisters come from:

• Sudden pinching or crushing

• Repeated rubbing or pressure (like from tight shoes or using tools)

• Accidentally biting the cheek or tongue
  In some cases, people with delicate skin, diabetes, or certain health conditions might get them more easily.

Is it safe to pop it?
No. Popping a blood blister can lead to infection. The skin over it helps protect the area while it heals. If it breaks on its own, gently wash it, apply an antiseptic, and cover it with a clean bandage.

How to treat it at home:

• Keep pressure off the area.

• Use a cold compress to reduce swelling.

• Wear comfortable, well-fitting shoes or gloves if needed.

• Keep it clean and dry.

When to see a doctor:
Contact a healthcare provider if:

• The blister is very painful, growing, or shows signs of infection (redness, warmth, pus).

• You get blood blisters often without an obvious cause.

• You have diabetes or circulation issues.

• It doesn’t start to heal within two weeks.

Most blood blisters go away on their own with time and simple care. Still, paying attention to your body—and knowing when to seek help—is always the safest choice.