What Is a Blood Blister? Symptoms, Causes, Treatment, and Prevention

If you develop a red, painful bump on your skin, it could be a blood blister. But how can you tell? And is a blood blister something to worry about? Here’s what blood blisters look like, their causes, and what to do about them.
What Is a Blood Blister? Definition Blood blisters are raised bumps or pockets of skin that form to protect an area after injury. They occur when the skin is pinched (as when closing a drawer on your finger or stubbing your toe), and the pocket fills with blood from broken blood vessels. The blood is what gives them a darker color with a distinctive red, purple, or black hue.e60dc2a1-f33c-4a05-9b50-8e3e8e597629faa37e17-7a95-4771-b19d-e75096393e22 While blood blisters often develop due to injury, certain medications and conditions can cause them, too. A blood blister can develop on different parts of the body. The most common spots include:e60dc2a1-f33c-4a05-9b50-8e3e8e597629faa37e17-7a95-4771-b19d-e75096393e22 Fingers Hands Toes Feet Blood blisters may also appear in and around your mouth, eyes, or genital area, though these areas are less uncommon and may signal an underlying health condition.e60dc2a1-f33c-4a05-9b50-8e3e8e597629faa37e17-7a95-4771-b19d-e75096393e22
Signs and Symptoms of a Blood Blister Symptoms The color distinguishes a blood blister from a standard friction blister. Friction blisters occur from constant pressure or rubbing, such as when wearing shoes that are too tight. They are filled with clear fluid called serum, which leaks in from nearby tissues as a reaction to skin injury.e60dc2a1-f33c-4a05-9b50-8e3e8e597629dce15581-220b-4b4a-b030-e159a1d0fa93 A blood blister looks red due to the blood inside.e60dc2a1-f33c-4a05-9b50-8e3e8e5976290dc29079-6b3d-4c71-80ac-5f638ac9c97d A blood blister changes in appearance over time. “When the blood blister is fresh (or recent), the blood is redder in color because it’s also fresh,” explains Anna Chacon, MD, a dermatologist based in Miami. As blood trapped under the skin ages, the blister darkens, turning dark red, purple, or even black, says Dr. Chacon. This color change is part of the healing process as the body reabsorbs the blood. Blood blisters can also vary in size, with some causing itching. The affected area can feel warm or sore to the touch, notes Chacon.
Causes and Risk Factors for a Blood Blister Causes Blisters are one of the body’s responses to injury. With a typical friction blister, only clear fluid collects under the skin. A blood blister, also referred to as a pinched injury, occurs when the skin is pinched yet the surface isn’t broken, Chacon explains. This results in a broken blood vessel that causes blood to pool under the skin.e60dc2a1-f33c-4a05-9b50-8e3e8e597629d5026a75-3610-492b-9ce3-52df46d13996 Risk factors for a blood blister include: Injuries If you hit your toe on an object, bump your hand or another body part, or close your finger in a drawer or door a blood blister can develop as an injury response.e60dc2a1-f33c-4a05-9b50-8e3e8e597629d5026a75-3610-492b-9ce3-52df46d13996 Medications Blood blisters can be common in people taking blood thinners because these medications make it harder for their blood to clot, so even a minor trauma can cause blood to pool under the skin, says Hannah Kopelman, DO , a dermatologist at Kopelman Hair Restoration in New York City. Medical conditions Diabetes and high blood pressure (hypertension) can also contribute to blood blisters due to poor circulation and fragile blood vessels, Dr. Kopelman says. Blood blisters in and around your mouth can be caused by other medical conditions, including oral cancer , rheumatoid arthritis , blood disorders, or kidney failure.e60dc2a1-f33c-4a05-9b50-8e3e8e597629d5026a75-3610-492b-9ce3-52df46d13996
How Is a Blood Blister Diagnosed? Diagnosis Blood blisters typically don’t require a visit to the doctor, as they’re often caused by a minor injury.e60dc2a1-f33c-4a05-9b50-8e3e8e597629689929d5-033b-411d-b9b8-7f1693bdb2e7 See your doctor if your blood blister doesn’t improve within a week, appears infected (your skin looks red and swollen, and the blister fills with white, yellow, or green fluid), is very painful or keeps returning, or is in an unusual place (such as the eye, mouth, or genitals).e60dc2a1-f33c-4a05-9b50-8e3e8e597629689929d5-033b-411d-b9b8-7f1693bdb2e7 There’s no specific test to diagnose a blood blister — doctors can identify it through a visual examination. Your doctor may take a fluid sample from the blood blister if there’s concern of an infection or other serious cause, notes Mary Alice Mina, MD , a dermatologist at Baucom & Mina Derm Surgery in Atlanta. “If a blood blister forms in an unusual area, such as around the eyes, mouth, or genital region, a fluid sample can help rule out more serious conditions,” explains Kopelman. For example, a fluid sample from a blood blister in the mouth may be tested for signs of oral cancer or infections. For blood blisters in the eyes or genital region, a sample can help identify underlying skin conditions, autoimmune disorders, or infections that contributed to the blister’s formation, Kopelman says.
How Long Does a Blood Blister Last? Duration Since blood blisters typically result from an injury, they often heal on their own in about a week, explains Dr. Mina. Blood blisters form under the epidermis, the outermost layer of skin where new skin cells grow.e60dc2a1-f33c-4a05-9b50-8e3e8e5976291575aa88-a9af-4df6-9f7b-981424591d1f As skin new cells develop and your skin heals, the blood gradually dries out and the blister fades away.e60dc2a1-f33c-4a05-9b50-8e3e8e597629295cf621-92a1-4cd5-895d-902709a70e49 See your doctor if you notice signs of infection, which include redness, pus, or increased pain or swelling.e60dc2a1-f33c-4a05-9b50-8e3e8e597629c1604626-c215-4dcd-bb0b-4dbabc763d6c
Treatment and Medication Options for a Blood Blister Treatment The ideal treatment for a blood blister is to allow the blister to heal on its own.e60dc2a1-f33c-4a05-9b50-8e3e8e59762981406898-11ce-442a-94e5-da6d308ec367 Do not try to pop or take the top off a blood blister, as this could lead to a skin infection, says Mina. To prevent further injury or irritation while the blood blister heals, keep the area clean and covered. First, gently wash the blister with mild soap and warm water before applying antibacterial ointment to reduce infection risk. Then, cover the blister with a bandage or nonstick gauze.e60dc2a1-f33c-4a05-9b50-8e3e8e597629b086a532-5bc5-4dc8-aa08-b5b32de82a04 In addition to covering the blister with a bandage, avoid activities that put pressure on it. For example, if you develop blisters on your feet , remove your shoes whenever possible or wear another pair until the blisters heal.e60dc2a1-f33c-4a05-9b50-8e3e8e5976292767c5f3-0ad4-4e5e-a3b6-3fd0ffc4c97c If you experience pain, ice the area or take over-the-counter pain relievers like acetaminophen or ibuprofen .e60dc2a1-f33c-4a05-9b50-8e3e8e597629633513bd-0418-4f7b-a1af-365824590875
Prevention of Blood Blisters Prevention You can’t always prevent injury, but understanding the risk factors for blood blisters and taking necessary precautions can help reduce their occurrence. The key to preventing blood blisters is to minimize friction and pinching the skin. Here are a few steps you can take:e60dc2a1-f33c-4a05-9b50-8e3e8e597629e58ca5ee-ae7e-47cb-a762-e2f6820024fb Wear properly fitted shoes to avoid pinching and pressure on your feet. Use protective gloves when working with tools or heavy objects. Add padding inside your shoes if you feel pressure in specific areas. Be careful when opening drawers and heavy doors and drawers to prevent fingers from getting caught.
Complications of Blood Blisters Complications While blood blisters usually heal on their own, some can become infected if bacteria enters through a break in the skin. Signs of infection can include increased redness, warmth, pus, or a foul odor, notes Kopelman.e60dc2a1-f33c-4a05-9b50-8e3e8e597629fcf19bb5-e0a1-412c-9009-d5b5aed75664 Seek medical attention if you notice these symptoms. An infected blood blister could lead to a skin or blood infection if left untreated.e60dc2a1-f33c-4a05-9b50-8e3e8e5976296904452c-6fa5-4c5d-9f50-03d9a63da453 A blood blister in the mouth, eye, or genital area can be caused by health conditions such as type 2 diabetes, high blood pressure, or autoimmune diseases . See your healthcare provider for diagnosis and treatment options.e60dc2a1-f33c-4a05-9b50-8e3e8e597629828aa51e-05b5-48f5-af0b-744933bc1fad
The Takeaway Blood blisters form when blood vessels under the skin break, filling the pocket of skin with blood. While they often resolve without treatment, complications like infection can occur, causing redness, swelling, or pus. Seek medical attention if you notice signs of infection, the blister doesn’t improve, or the blister develops on your eye, mouth, or genitals.