It pays to have a healthy respect for blood blisters as they pose a heightened risk for infection. But do you know what makes a blood blister or black toenails? How do you deal with them? Do you pop them or not? And how long will they take to heal?

Summary

Blood Blister Do’s

  1. Get the pressure off (or down)
  2. Stop the skin stretching and tearing by reducing friction!
  3. Be clean, use antiseptic and a sterile non-adherent dressings to protect from infection

Blood Blister Don’ts

  1. Don’t just ignore it and keep going or it will tear and be open to infection
  2. Don’t ignore the benefits of lancing it (but only if the situation is right!)
  3. Don’t neglect pressure relief and friction relief

FAQs About Blood Blisters

1. What causes a blood blister?

The presence of blood in a blister indicates there is high pressure component. It’s this high pressure that causes deeper injury – injury to small blood vessels in the dermis. Blood then tracks into the epidermis and mixes with the normal blister fluid. That’s why blood blisters often occur over joints and bony prominences: like the back of the heel, the toes and the metatarsal heads (ball of the foot).

blister skin layers

Blood vessels exist in the dermis, not the epidermis where blisters form. That’s why normal blisters are not filled with blood.

2. What colour are blood blisters?

In the initial stages, a blood blister looks red. Then as the blood dries and coagulates over time, is goes a purple or black. You can read more about the colours of blisters here.

If you notice a black spot on your foot, be mindful there are other diagnoses for this. Of highest importance would be melanoma, particularly nodular melanoma. If there has been no trauma to have caused a blood blister, please consult your doctor to rule out melanoma.

3. How long does a blood blister take to disappear?

Blood stains the skin cells it comes in contact with. It can take a month or more for that discolouration to disappear. We know it takes somewhere from 30 to 48 days for full epidermal cell turnover – that is for cells to travel from their deepest to most superfical, to be shed as dead skin cells. So it could take that long before all trace disappears. The blood will dry relatively quickly, assuming you take away the cause. If you don’t deal with the cause, your blood blister will last longer. 

There may be a lot of black dried blood that flakes away. Or there may be just a little.

  • It depends on how much blood there was initially.
  • It depends on how much of the blood resorbed.
  • And it depends on whether you reduce the excess pressure or not – it may be a perpetual blood blister if you don’t do anything to stop it from forming.

Blood Blister Causes

Structural causes of blood blisters

Bony prominences are at most risk, like a bunion for example. Your forefoot is wider when you have a bunion. However, it’s not necessarily the bunion protuberance itself at most risk of developing a blood blister. It’s the weightbearing undersurface that’s at risk. There’s a concentration of pressure as the prominent joint bulges over the sole of the shoe. Coupled with high friction, there’s a blood blister waiting to happen.

blood blister edge of forefoot

Edge Blood blister under a callous in the presence of a bunion (image credit: Sue’s Ramblings). You can read more about edge blisters here.

toe blood blister

Toe blood blister

Biomechanical causes of blood blisters

The blood blisters under the big toes in the first image of this article are a consequence of the foot’s biomechanics. There’s an important function of the 1st MPJ (big toe knuckle) called the windlass mechanism. When it’s not working adequately, there can be extremely high pressure under the joint of the big toe – where these blisters are.

peak pressure under foot

Functional hallux limitus (inefficient windlass mechanism) as a cause of blood blisters under the big toe.

The best way to deal with this is with to see a Podiatrist because they know how to facilitate the windlass mechanism – treatment will likely include orthotics and calf stretches and maybe some other things, depending on where you’re getting blood blisters.

 

Treating Blood Blisters on the Feet

If you miss the blister prevention boat and end up with a blood blister, follow the normal blister treatment sequence to get rid of that foot blisters. But now, preventing infection really is your priority! As a result, consider the options below, depending on your blister location, the environment you’re in and what gear you have access to. 

Blood blister treatment can include:

a) Taking away all pressure

If it’s possible, remove all pressure to ensure the blister roof remains intact and allow it to heal in its own time. For example, a blood blister on top of your toe would benefit from simply wearing open-toed sandals. Similarly, a blister at the back of your heel would get relief from wearing open-backed scuffs. However, barefeet, or complete nonweightbearing may be your only option, depending where your blood blister is. Either way, by taking away all pressure, the blister remains intact with no chance of infection.

But if your blood blister is on the weightbearing area of the foot, or you have to wear shoes, it’s not quite so simple. 

b) Reducing some pressure AND cutting friction levels

There are parts of your foot where taking away all pressure might not be possible – like under the ball of the foot. And there are times when you just have to keep going. At this point, this is where pressure deflection can help in conjunction with reducing friction levels.

You can do this with a donut pad, like the image below. This one’s very thin though. To provide better pressure deflection, use a thicker material like podiatry felt.

donut pad

Moleskin donut pad (Getty Images)

  • Reduce pressure with donut pads cut from thick adhesive orthopedic felt. The idea is you place the cavity over your blister to keep the pressure off it.
  • Reduce friction levels with Engo Blister Patches. You stick these to your shoe or insole to stop the skin stretching (shearing) and tearing the capillaries further.

Popping Your Blood Blister

There are times when keeping the blister roof intact is not the best option. It can be better to take matters into your own hands rather than ignore it and simply hope for the best. If you have the right equipment, you could deal with this appropriately and safely. It sure beats putting your blood blister with roof intact back into your shoe with no dressing and no pressure relief, therefore just leaving it to chance. 

However, please realise the risk of bacterial infection when you open up a blister. For the following few days, you’ll need to be on the watch for signs of blister infection which include redness, swelling, pain and pus. Moreover, if you notice red streaks extending from your blister up your leg, this is serious and you need urgent medical attention. 

Okay, so you’ve decided you want to lance your blood blister. Perhaps the amount of blood accumulating is causing pain; perhaps the blister is too big and likely to tear anyway; perhaps you have to carry on running or hiking and need this blister deflated. These are all legitimate reasons to po a blood blister… but only if you have the right gear! (One more time, remember, it is okay to not lance your blood blister. In other words, if in doubt, don’t pop it! Read this article to help you decide if to lance or leave alone). 

The Equipment You’ll Need

If you are going to lance your blister, here’s what you’ll need to do it so it doesn’t hurt and to avoid infection (below). This is a great little kit. We call it the Sterile Blister Lance Pack and we sell it from our online store. With expedited shipping, you could have one of these in your hands tomorrow so you can start looking after your blood blisters, infection-free. There are enough items in this pack to provide 4 blister lancing and treatment episodes.

 

Plus, I’ve included easy to follow instructions to help you every step of the way in lancing your blister safely and painlessly.  

On a related note, if you’ve got a black toenail, here’s how to treat it by drilling the nail. You can use the hypodermic needles in the Sterile Blister Lance Pack to perform this procedure.

Blood Blister On Toe Or Finger

Whether you’ve got a blood blister on your toe or your finger, the principles of treatment are the same. It’s trickier on the feet though – not least of which is because we have to stand, walk and run on them. Our feet are subject to high weightbearing pressures and high contact pressures from footwear. As a result, these forces can undo any healing we are trying to facilitate with our treatment.

The other main difference between foot and finger blood blisters is our feet are generally a more germy environment, and so they’re more susceptible to infection. Think about it… our feet keep us in contact with the ground, which is a germy environment. Then we cover them in socks and shoes and keep them out of sight. Think about the warm, humid and dark environment they live in.

I trust the tips and techniques discussed in this article can help heal your blood blister. Please note that I am a podiatrist. In other words, I provide information about foot blisters (not blood blisters on legs, hands, the face or elsewhere).