A blood blister can look alarming at first glance—a dark red or purple bubble under the skin that appears suddenly and often without warning. While they’re usually harmless, blood blisters can be uncomfortable and, in some cases, signal that something more is going on. Understanding what blood blisters are and how to handle them can help you treat them safely and know when to seek medical advice.

What Is a Blood Blister?

A blood blister forms when small blood vessels (capillaries) beneath the skin rupture but the skin itself remains intact. Blood becomes trapped under the surface, creating a raised, fluid-filled pocket that appears red, maroon, or purple—darker than a typical clear blister.

Blood blisters most commonly appear on:

Fingers and palms

Toes and soles of the feet

Inside the mouth (cheeks, tongue, or gums)

Common Causes of Blood Blisters

Most blood blisters are caused by sudden pinching or repeated friction, such as:

Slamming a finger in a door

Wearing tight or poorly fitting shoes

Using tools or sports equipment without protection

Repetitive motions that create pressure on the skin

Blood blisters in the mouth can result from:

Accidental biting

Dental procedures

Sharp or poorly fitting dental appliances

In some cases, blood blisters may appear more easily in people with:

Thin or fragile skin

Circulation issues

Diabetes

Certain blood or clotting disorders

Symptoms to Expect

A blood blister may cause:

A raised, bubble-like area under the skin

Dark red, purple, or black coloring

Tenderness or pressure pain

Occasional swelling around the area

Most blood blisters are not dangerous and heal on their own within one to two weeks.

Should You Pop a Blood Blister?

In most cases, no. The intact skin over a blood blister acts as a natural barrier against infection. Popping it increases the risk of bacteria entering the wound and can slow healing.

If a blood blister bursts on its own:

Gently clean the area with soap and water

Apply an antiseptic

Cover with a sterile bandage

Keep the area clean and dry

How to Treat a Blood Blister at Home

For uncomplicated blood blisters:

Reduce pressure or friction on the area

Apply a cold compress for 10–15 minutes to reduce swelling

Keep the blister clean and protected

Wear properly fitting footwear or gloves if needed

Avoid harsh chemicals or home remedies that can irritate the skin.

Blood Blisters in the Mouth

Oral blood blisters often heal quickly but can be painful. Rinsing with warm salt water can help reduce irritation and keep the area clean. Avoid hot, spicy, or sharp foods until healing occurs.

If blood blisters in the mouth appear frequently or without injury, it may be worth discussing with a dentist or doctor.

When to See a Doctor

Seek medical advice if:

The blood blister is extremely painful or growing

There are signs of infection (redness, warmth, pus, fever)

Blood blisters appear repeatedly without clear cause

You have diabetes, poor circulation, or a bleeding disorder

Healing takes longer than two weeks

Rarely, recurring or unexplained blood blisters can be linked to underlying medical conditions that require evaluation.

Can Blood Blisters Be Prevented?

You can reduce your risk by:

Wearing well-fitting shoes and protective gloves

Cushioning tools or sports equipment

Keeping skin moisturized to prevent cracking

Managing underlying health conditions effectively

Final Thoughts

Blood blisters are usually minor injuries caused by pressure or friction and typically heal without treatment. While they can look concerning, most are harmless and temporary. Paying attention to how and where they form—and how often—can help you determine whether simple care is enough or if a medical checkup is needed.

If in doubt, especially when blood blisters are frequent or slow to heal, it’s always best to seek professional advice rather than ignore a potential warning sign from your body.