What blood blisters are
Blood blisters can appear suddenly and often look alarming because of their dark red or purple color. In most cases, however, they are harmless. They occur when small blood vessels under the skin break while the outer skin remains intact. As the article explains, “they form when small blood vessels beneath the skin rupture while the outer layer of skin remains intact.” The trapped blood creates a raised bubble that usually heals on its own.

Common causes and locations
Blood blisters usually develop after pressure, friction, or minor injuries. They often appear on the hands, fingers, feet, or toes because these areas experience frequent rubbing or impact. Tight shoes, repetitive tasks, or pinching injuries such as slamming a finger in a door can cause them. Blood blisters can also appear in the mouth, often after accidental biting or irritation from dental appliances.

Symptoms and healing
A blood blister typically begins as a small raised spot that may feel tender. Over time it may appear dark red, purple, or almost black due to the trapped blood. Although they may look serious, most blood blisters gradually shrink as the body reabsorbs the blood and repairs the skin.

Basic care and treatment
In most cases, blood blisters do not require special treatment. It is generally best not to pop them because the intact skin protects the area from infection. Instead, keep the blister clean, reduce pressure on the area, and allow it to heal naturally. The article notes that “the intact skin covering the blister acts as a natural protective barrier against bacteria.”

When to seek medical advice
While most blood blisters heal within one to two weeks, medical care may be needed if the blister becomes very painful, grows larger, or shows signs of infection such as redness or pus. People with certain health conditions, including diabetes or circulation problems, should be especially cautious and monitor any skin injuries carefully.