We’ve all been there. You pinch your finger in a drawer, wear a pair of shoes that rub the wrong way or drop something heavy on your toe. At first, you feel pain and a little swelling. Then you notice a dark red, purple or black bubble under your skin. You have a blood blister.
For most people, a blood blister isn't dangerous. It’s your body’s way of protecting the injured skin below but it sure doesn’t look great. Here’s what you need to know, based on trusted medical advice.
What is a blood blister?
A blood blister is a raised area of skin that forms when small blood vessels (capillaries) break under the skin’s surface.
“Unlike a regular blister which contains clear fluid, a blood blister contains blood. This gives it a darker appearance,” said Samia Kadri, a family nurse practitioner at Banner Urgent Care. “Depending on the amount of blood inside, it may look red, purple, dark brown or black.”
Blood blisters often develop when the skin is:
- Pinched
- Crushed
- Exposed to repeated friction
- Injured by pressure
Common places where blood blisters appear include:
- Heels and soles of the feet
- Fingers and toes
- Inside the mouth
- Under fingernails or toenails (called subungual bleeding)
Common causes of blood blisters
“Blood blisters typically develop when the skin experiences repeated friction or direct pressure,” Kadri said. “A blood blister on a foot is especially common in runners, hikers and people who spend long hours standing.”
Common causes include:
- Friction from shoes: Shoes that are too tight, too loose or don’t fit well can rub against your skin and cause irritation. This often leads to blood blisters on the toes, heels or other parts of your foot.
- Sweat and moisture: When your feet sweat a lot, the skin becomes softer and more likely to get irritated. This can make blisters more likely to form.
- Repetitive pressure: Doing the same activity repeatedly, like walking long distances, running or using tools, can hurt your skin and break tiny blood vessels.
- Pinching or crushing injuries: Getting your finger caught in a door, bumping your toe against a hard surface or other small injuries can break blood vessels and cause a blood blister.
- Burns: Heat, including some friction burns, can damage the skin and lead to blister formation.
- Trauma or impact: A direct hit or sudden injury to the skin can cause blood to pool underneath surface layers.
- Certain medical conditions: Problems like diabetes or nerve issues can affect your skin, blood flow or healing. These conditions may increase the chance of blisters or slow down their healing.
Why you shouldn’t pop a blood blister
When you see a blood blister, your first instinct might be to drain it. However, doing so can create more problems than it solves.
The American Academy of Dermatology recommends not popping or draining blisters. If you do, you can:
- Increase the risk of infection
- Slow down healing
- Cause additional pain
- Develop scars
- Expose sensitive tissue underneath
“The skin covering the blister is there for a reason,” Kadri said. “It acts like a natural bandage. As your body heals, it gradually absorbs the blood and fluid inside.”
How to care for a blood blister
Most blood blisters can be treated at home with basic first aid. The goal is to protect the blister and prevent further irritation.
- Keep the area clean: Wash the area gently with soap and water. Avoid scrubbing the blister or using harsh products that may irritate the skin.
- Protect it from friction: If the blister is in an area that rubs against shoes, clothing or tools, cover it with a clean bandage. A loose, protective dressing can help reduce irritation while the skin heals.
- Reduce pain and swelling: If the area is painful, apply a cool compress wrapped in a cloth for 10 to 15 minutes at a time. You can repeat this as needed during the first day after the injury.
- Avoid pressure: Try to avoid activities that put pressure on the blister. For example, wear comfortable shoes if the blister is on your foot or protective gloves if it is on your hand.
- Elevate the area if possible: Keeping the injured area elevated may help reduce swelling.
- Leave it alone: This may be the hardest step but it is often the most important. Avoid picking at the blister, squeezing it or trying to drain it. Most blood blisters heal within one to two weeks.
What about a blood blister under a nail?
A blood blister under the fingernail or toenail can be especially painful. In some cases, the pressure under the nail becomes severe enough that a health care provider may recommend draining it to relieve pain. However, this should be done by a medical professional. Do not attempt to do this on your own.
What if a blood blister breaks on its own?
Sometimes a blood blister opens naturally, especially if it’s in an area exposed to repeated friction. If this happens, don’t panic.
Take these steps:
- Wash your hands
- Gently clean the area with soap and lukewarm water
- Apply an antibiotic ointment, such as bacitracin
- Cover it with a clean, non-stick bandage
- Change the dressing if it becomes wet or dirty
You should avoid:
- Pulling off the skin
- Using alcohol on the wound
- Using hydrogen peroxide
- Applying tight bandages
- Touching the area with unwashed hands
How can you tell if a blood blister is infected?
Most blood blisters heal without complications. But it’s important to watch for signs of a blood blister infection.
Signs of infection:
- Increasing redness around the blister
- Warmth in the surrounding skin
- Swelling that is getting worse
- Pus or cloudy drainage
- Worsening pain
- Fever
- Red streaks spreading away from the blister
See your health care provider if:
- The blister is larger than about one inch
- It interferes with walking, standing, gripping or daily activities
- You have signs of infection
- It isn't improving after one to two weeks
- It keeps returning in the same spot
- Multiple blisters appear without a clear cause
- A burn or chemical exposure caused the injury
- You have diabetes, an autoimmune condition or other chronic health conditions
“If you have diabetes, neuropathy or poor circulation, even a small blister can become a big problem if it isn’t monitored carefully,” Kadri said. “These conditions can make it harder for your body to heal and increase the risk of infection.”
Seek urgent medical care if you experience:
- Severe pain
- Fever
- Significant swelling
- Possible fracture
- Loss of feeling in the area
- Signs of a spreading infection
- A blood blister from a serious burn
Can you prevent blood blisters?
You can’t prevent every injury but a few simple steps can reduce your risk.
Prevention tips:
- Wear shoes that fit well.
- Break in new shoes gradually
- Use moisture-wicking socks
- Add padding or moleskin to areas that rub
- Wear gloves for yardwork, tools, sports or lifting
- Avoid pinching skin in doors, drawers or equipment
- Use protective gear for sports and exercise
- Stop activity if you feel rubbing, pinching or a hot spot
- Keep feet dry
- Check your feet after long walks, hikes or sports
- If you have diabetes, inspect your feet daily and avoid going barefoot
The bottom line
If you’re wondering, “Should I pop a blood blister?” the answer is usually no. Although it may be tempting, leaving the blister intact is often the safest and fastest path to healing.
Keep the area clean, protect it from further friction and give your body time to heal. In most cases, the blister will gradually disappear on its own.
If you notice signs of infection, pain or delayed healing, check in with a health care provider or a Banner Health specialist. Otherwise, a little patience is often the best treatment.
Frequently Asked Questions
Is it a bad idea to pop a blood blister?
Yes, in most cases. Popping a blood blister can increase the risk of infection, slow healing and cause more pain or bleeding.
Will a blood blister go away on its own?
Most blood blisters heal on their own. The body gradually absorbs the blood while the skin underneath repairs itself.
How long does a blood blister take to heal?
Many blood blisters improve within one to two weeks, depending on size, location and whether the area is protected from friction.
What should I put on a blood blister?
Keep it clean and cover it with a loose, nonstick bandage if it may rub against clothing. Use padding around the blister to reduce pressure.
What if a blood blister pops by itself?
Clean it gently with soap and water, leave the skin flap in place if possible, cover it with a clean bandage and watch for infection.
Should I drain a blood blister under my toenail?
Do not try to drain a painful blood blister or blood under a nail at home. A provider can check for injury and, if needed, drain it safely.
Can a blood blister get infected?
Yes. Signs of infection include spreading redness, warmth, swelling, worsening pain, pus, red streaks or fever.
Should people with diabetes pop blood blisters?
No. People with diabetes should never pop blood blisters, especially on the feet. Contact a provider because blisters can worsen or become infected. Here are tips for diabetes wound care.
