What is a blood blister? Causes, treatment and prevention.

What causes blood blisters?

A blood blister forms when small blood vessels, called capillaries, break under the skin's surface. Unlike a regular blister, which is filled with clear fluid, a blood blister fills with blood due to this internal damage. 

This happens when the skin is pinched, pressed, or irritated, but the surface doesn’t break open.

Common scenarios that lead to blood blisters include:

• Friction. Tight shoes, repetitive rubbing, or poorly fitted gloves can create enough pressure to form a blister.
• Trauma. A sharp pinch or sudden impact, like closing your finger in a door, can break the blood vessels without cutting the skin.
• Skin conditions. Certain medical conditions, like eczema or dermatitis, can make your skin more prone to irritation and blisters.
   

Common triggers of blood blisters.

Blood blisters can appear almost anywhere on the body, but some areas are more prone than others. Recognizing these triggers can help you avoid them in the future.
 

1. Ill-fitting footwear.
   Wearing shoes that are too tight or rub against your feet can create the perfect storm for blood blisters, especially on your heels and toes.
2. Sports and physical activity.
   High-friction activities, like running or weightlifting, can put pressure on your hands and feet. Without proper protection, this can lead to blisters.
3. Accidental trauma.
   Slamming your finger in a drawer or catching your hand on a sharp edge can easily cause a blood blister.
4. Medical treatments or conditions.
   Some people are more prone to blood blisters due to sensitive skin or certain treatments, like radiation therapy, which can make the skin more fragile.
    

How to care for a blood blister without popping it.

When you notice a blood blister, you might want to pop it. But leaving it intact is the best course of action. A blood blister acts as a natural barrier and protects the damaged area underneath from infection.

Here’s how to care for it properly.

1. Clean the area gently.
   Wash the blister and the surrounding skin with mild soap and warm water. Keeping the area clean helps prevent bacteria from getting in and causing an infection.
2. Protect it with a bandage.
   Cover the blood blister with a loose, sterile bandage. This adds an extra layer of protection and prevents friction that could cause the blister to pop on its own.
3. Avoid pressure or friction.
   Try not to put pressure on the blister. For example, if the blister is on your foot, avoid tight shoes that could rub against it. Letting it heal undisturbed is key.
4. Don’t pop it.
   Popping a blood blister can introduce bacteria into the wound, increasing the risk of infection. The fluid inside helps the skin heal naturally, so it’s best to leave it alone.
5. Apply a cold compress if needed.
   If the blister is painful or swollen, a cold compress can provide relief. Wrap an ice pack in a cloth and apply it to the area for a few minutes at a time to reduce inflammation.

When to see a doctor for blood blisters.

Most blood blisters heal on their own within a week or two, but if you notice any signs of infection—such as redness, warmth, pus, or increasing pain—it’s time to see a healthcare provider. An infected blister may require professional care to prevent complications.

By following these steps, you can help your blood blister heal safely and effectively, reducing discomfort while avoiding unnecessary risks. Prevention, of course, is the best approach—so taking steps to avoid the common causes of blood blisters can help you steer clear of them altogether.

How long do blood blisters last?

Most blood blisters heal on their own within one to two weeks. During this time, the body gradually reabsorbs the trapped blood and the skin layer covering the blister dries up and falls off naturally.

The healing process can vary depending on factors like:

• The size of the blood blister. Larger blood blisters may take longer to heal.
• The location of the blood blister. Blisters in high-friction areas like the feet may take longer if they’re repeatedly irritated.
• How well you care for it. Proper cleaning, protection and minimizing pressure can speed up recovery.

See a healthcare provider if the blister remains tender or doesn’t improve within two weeks. Persistent blisters may indicate an underlying issue, such as a skin infection or poor circulation.

Take care of your skin with CityMD.

Blood blisters are usually harmless and heal with a little care and patience. Protecting the blister, avoiding unnecessary pressure and keeping the area clean can prevent complications and speed up healing.

But if your blood blister isn’t healing, becomes infected, or causes significant pain, it’s important to seek medical attention. At CityMD, our skilled providers are here to assess your concerns and offer expert treatment.

Don’t let a simple blister turn into a bigger issue. Stop by your nearest CityMD location for convenient, walk-in care—no appointment necessary. Let us help you get back to feeling your best!