What is a blood blister?
A blood blister is a blister that fills with blood instead of clear liquid. Blisters are small pockets of fluid under a layer of skin. Your skin has three layers. The outermost layer is the epidermis, the middle layer is the dermis and the bottom layer is the hypodermis. A blister forms under the epidermis layer. It fills with clear liquid or blood, depending on the injury that damaged your skin. Blood blisters occur when you’ve also damaged the blood vessels in your skin. Your immune system responds to the damage and inflammation occurs.
Blood blisters are most common on your hands, fingers, feet and toes. You may get them near your joints and on bony areas such as the heels and balls of your feet. Blood blisters on your skin typically heal on their own. Blood blisters in and around your mouth, such as the inside of your cheek and on your lips, can have more serious causes. You should see your healthcare provider if a blood blister develops anywhere in your mouth.
Symptoms and Causes
What does a blood blister look like?
Blood blisters are raised pockets of skin that look like friction blisters. But blood blisters appear red, purple or black because they’re filled with blood instead of clear fluid. The blood starts as a light red color and becomes darker over time. Blood blisters can range in size.
You may feel pain or discomfort in the area of the blister due to the injury that caused it. Sometimes blood blisters can cause itching as well.
What causes a blood blister?
You can get a blood blister when something pinches your skin but doesn’t break it open. Instead of clear liquid, blood floods the area from broken blood vessels and damage to the lower layers of your skin. The blood pools and forms a blister. Blisters develop to protect your damaged skin and help it heal.
You may get a blood blister after closing a drawer on your finger or stubbing your toe on the ground. Sweaty feet can cause friction against your feet and toes. Severe frostbite can also cause blood blisters. Certain medications such as blood thinners may cause blood blisters as well.
A condition called angina bullosa hemorrhagica can cause blood blisters in your mouth. With this condition, a painful, blood-filled blister develops on your tongue, gums or the floor of your mouth. Angina bullosa hemorrhagica is a noncancerous (benign) condition. The blister usually bursts on its own and no treatment is needed.
But blood blisters in and around your mouth may be caused by more serious conditions. These conditions may include:
Diagnosis and Tests
How is a blood blister diagnosed?
You usually don’t need to see your healthcare provider for a blood blister. But if you see your healthcare provider, they can probably tell you have a blood blister by looking at it. There aren’t any tests to diagnose a blood blister.
Your healthcare provider will look over the area and make sure it’s not infected. If the blood blister is in your mouth, eye, genital area or another unusual place, they may take a biopsy. A biopsy takes a sample of the blister’s fluid for testing.
Management and Treatment
How do you treat a blood blister?
Blood blisters typically heal on their own within a week. They heal as new skin grows below the blister’s raised layer and the blood in the blister dries out. But if you want to get rid of a blood blister faster, you can try these steps:
- After washing your hands, gently wash the blood blister with mild soap and water.
- Apply an antibacterial cream or ointment onto the blood blister.
- Place a bandage or gauze over the blood blister to protect the area.
Make sure to change your bandage at least once a day. Keep the area clean and dry.
You should never try to pop a blood blister or peel away the skin around it. The skin over the blood blister protects deeper layers of your skin from getting infected.
How can I prevent blood blisters?
Blood blisters are usually the result of something pinching part of your skin. They often occur on your hands and feet. Steps to prevent blood blisters include:
- Staying alert when using tools or other objects that can pinch your skin.
- Wearing gloves when working with tools such as pruners or pliers that could pinch your skin.
- Protecting your feet and toes with socks and appropriate shoes.
- Using drying powder in your shoes to soak up moisture.
- Adding padding to your shoes if you’re feeling pressure.
Outlook / Prognosis
What can I expect if I have a blood blister?
Most blood blisters heal on their own within a week. Make sure to clean the blister, apply antibacterial cream and protect the site with a bandage while it heals. If you have a blood blister on your foot or toe, avoid wearing shoes if possible, or wear open-toe shoes to protect the blood blister. If you think your blood blister may be infected, call your healthcare provider.
When should I see my healthcare provider?
See your healthcare provider if your blood blister doesn’t improve within a week. You should also reach out to your healthcare provider if your blood blister appears infected. If your blood blister is infected, your skin will look red and swollen. The blister will fill with white, yellow or green pus rather than blood. Without treatment, an infected blood blister could lead to a skin or blood infection.
Also, reach out to your healthcare provider if you’ve developed:
- A blood blister that’s very painful or keeps returning.
- Several blood blisters for no apparent reason.
- A blood blister in your eye, mouth, genitals or another unusual place.
A note from Cleveland Clinic
Blood blisters are common skin conditions. While they can be unpleasant, they typically aren’t a cause for concern. If you get a blood blister, it should begin to heal on its own within a week. If your blood blister appears infected, see your healthcare provider. In addition, see your healthcare provider if you develop a blood blister in an unexpected place such as your mouth. While blood blisters develop for many reasons, it’s best to have your healthcare provider take a look.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy