A blister under your toenail, usually a pocket of blood trapped between the nail plate and the nail bed, is one of the more common and painful nail injuries. Treatment depends on its size and how much pain it causes. Small ones that don’t hurt much can be left alone and will grow out as the nail replaces itself over the next several months. Larger, painful ones often need to be drained through a small hole in the nail, a procedure called trephination, which brings rapid relief. The details of when to intervene, what you can safely do at home, and when you need professional help matter quite a bit for avoiding complications.
What Is Actually Happening Under the Nail
When you stub your toe hard, drop something on it, or wear shoes that slam your toenails during activity, blood vessels in the nail bed can rupture. The blood has nowhere to go because the nail plate is sitting right on top of it, so it pools in a thin layer and forms what doctors call a subungual hematoma. It looks like a dark red, purple, or blackish discoloration under the nail, and the pressure of that trapped blood against the sensitive nail bed is what causes the throbbing pain that can keep you awake at night.
Friction blisters filled with clear fluid can also form under toenails, though these are less common than the blood-filled variety. Runners and hikers sometimes get them from repetitive microtrauma as the toe slides forward in the shoe with each step. In either case, the underlying problem is the same: fluid is trapped in a space that doesn’t stretch, and pressure builds.
When You Can Treat It at Home
If the dark area under the nail covers a small portion of the nail surface and the pain is manageable, you probably don’t need any procedure. The blood will slowly be reabsorbed by your body or will simply grow out with the nail over the next few months. In the meantime, there are a few things worth doing:
- Elevate and ice: Keep your foot propped up and apply a cold pack wrapped in a thin cloth for 15 to 20 minutes at a time during the first day or two. This limits further swelling and bleeding.
- Protect the toe: Wear open-toed shoes or a shoe with a wide toe box to avoid putting more pressure on the nail. If you have to wear closed shoes, a small piece of padding or moleskin over the nail can help.
- Manage pain: Over-the-counter anti-inflammatory painkillers can help with both pain and swelling. Avoid aspirin if the injury is fresh, since it can promote further bleeding.
- Keep it clean: If the nail is cracked or the skin around it is broken, wash gently with soap and water and apply a thin layer of antibiotic ointment. Cover with a breathable bandage.
The key question is pressure. If the trapped blood is causing constant, intense throbbing, the hematoma likely needs to be drained rather than left alone. Pain that worsens over the first 24 to 48 hours is a strong signal that the pressure is too high for your body to deal with on its own.
How Drainage Works
Draining a subungual hematoma is one of the most immediately satisfying procedures in medicine, both for the person performing it and for the patient. A small hole is made in the nail plate directly over the blood collection, and the dark blood flows or is gently expressed out. The pain relief is often dramatic. One study using a controlled drill technique found substantial relief within hours of the procedure, with minimal discomfort and minimal risk of damaging the nail bed underneath.1PubMed. Controlled nail trephination for subungual hematoma
There are a few common methods clinicians use to create that hole:
- Heated paperclip or cautery device: A straightened paperclip is heated until it glows red-hot and gently pressed through the nail plate. The nail itself has no nerves, so this doesn’t hurt when done correctly. The heat melts through the nail, and the blood drains immediately. This is the classic method taught in emergency medicine.
- Needle or drill: A large-bore needle or a small handheld drill is used to bore through the nail mechanically rather than thermally. This approach offers more control and avoids any risk of thermal injury to the nail bed.
- Fine syringe needle: For smaller hematomas, especially on the smaller toes where the nail is thin, an extra-fine needle like those used for insulin injections can be twisted through the nail plate. Researchers have found this technique to be fast, simple, and well-tolerated, particularly effective for the second, third, and fourth toenails where traditional trephining methods are harder to use.2PubMed. Extra-fine insulin syringe needle: an excellent instrument for the evacuation of subungual hematoma
After the hole is made and the blood drains out, the area is typically cleaned with antiseptic and covered with a sterile bandage. You may be told to soak the toe in warm water once or twice a day for the next few days to keep the drainage hole open and allow any remaining blood to seep out. The hole in the nail will grow out naturally.
Should You Try Draining It Yourself?
You’ll find plenty of online tutorials showing people heating a paperclip and poking through their own toenail at home. It can work, and people do it. But the risks are real. The biggest concern is infection: you’re creating an opening through a protective barrier directly into tissue that sits right against bone. If your sterilization isn’t thorough, bacteria can get in. A badly placed hole can also damage the nail bed, which may cause the nail to grow back with a permanent ridge or deformity.
If you’re considering self-drainage, at minimum you should clean the toe thoroughly with antiseptic, use a sterilized instrument, and only pierce the nail over the darkest part of the hematoma where the blood pool is clearly visible. Stop as soon as you feel the resistance change, meaning you’ve passed through the nail plate, because pushing further will damage the nail bed beneath. And afterward, treat the site like an open wound: clean it, apply antibiotic ointment, and bandage it daily.
That said, if you have diabetes, peripheral neuropathy, a compromised immune system, or poor circulation in your feet, self-treatment is a bad idea. These conditions dramatically increase infection risk and slow healing. See a doctor instead.
Red Flags That Warrant a Doctor Visit
Not every blister under a toenail is a simple hematoma. Some situations call for professional evaluation regardless of whether the injury seems minor:
- Severe pain with a crushed or fractured toe: If the injury was high-force, like dropping something heavy, you could have a fracture of the distal phalanx (the toe bone directly under the nail). A fracture combined with a subungual hematoma is technically an open fracture if the nail bed is lacerated, and it may need more than just drainage.
- Hematoma covering most of the nail: When the blood pool takes up a large portion of the nail surface, the nail bed underneath may be significantly torn. Some clinicians recommend removing the nail entirely to inspect and repair the nail bed in these cases, to give the nail the best chance of growing back normally.
- Signs of infection: Increasing redness, warmth, swelling, pus, red streaking up the toe or foot, or fever in the days after the injury all suggest infection. Nail bed infections can progress to involve the bone, which is a serious complication. One case report documented a toe infection that progressed to involve the entire distal phalanx, ultimately requiring surgical removal of the bone.3PubMed Central. Rare case of Isolated Aspergillus Osteomyelitis of Toe: Presentation and Management
- Dark discoloration with no injury: If you notice a dark spot under the toenail that appeared without any trauma you can recall, it may not be blood at all. Subungual melanoma, a form of skin cancer, can mimic the appearance of a hematoma. It’s uncommon, but any unexplained dark streak or patch under the nail that doesn’t grow out over weeks deserves a dermatologist’s evaluation.
Nail Removal and When It Becomes Necessary
In most cases, the nail stays on. Trephination drains the blood, the pressure drops, and the nail acts as a natural splint for the healing nail bed underneath. But there are situations where partial or total nail avulsion, meaning removal of the nail, is the better option. Nail avulsion allows direct examination of the nail bed and nail matrix when a doctor suspects a laceration, a tumor, or an embedded infection that can’t be treated through the intact nail.4Indian Journal of Dermatology, Venereology and Leprology. Nail avulsion: indications and methods (surgical nail avulsion)
Nail removal sounds dramatic, but the procedure is done under local anesthesia and is relatively straightforward. The nail is gently separated from the nail bed, the underlying tissue is treated or repaired, and the toe is bandaged. Recovery is the slower part. After total nail removal, healing of the wound beneath the nail takes roughly five to seven weeks in most cases, and the nail itself takes anywhere from six to twelve months to regrow fully on a toenail. The new nail often looks normal, though some people end up with slight ridging or thickening if the nail matrix was damaged.
What Recovery Looks Like
If you had a simple drainage without nail removal, the recovery timeline is fairly short. Pain drops significantly within hours of the procedure, and the toe is usually back to feeling normal within a week or two. The hole in the nail grows out gradually, and you can expect the discolored portion of the nail to take three to six months to fully grow out since toenails grow slowly, roughly a millimeter or so per month.
During recovery, keep the toe clean and dry. Change bandages daily if you have a drainage site or any open area. Avoid tight shoes, and hold off on running, hiking, or other activities that pound the toes until the pain is completely gone. If the nail loosens and starts to lift away from the nail bed in the weeks after injury, don’t panic and don’t pull it off. Let it separate on its own or have a doctor trim it. A new nail is usually already forming underneath.
Wound care after nail surgery matters more than people expect. Even something as simple as the type of dressing used can influence healing time. Research comparing different wound dressings after toenail surgery found that healing times averaged around five to six weeks after total nail removal, with some variation depending on the dressing type.5Journal of Wound Care. Honey dressing versus paraffin tulle gras following toenail surgery The point is that these wounds don’t heal overnight, and consistent daily wound care during that window prevents complications.
Preventing Subungual Blisters in the First Place
Most subungual hematomas come from one of two sources: a single hard impact or repetitive low-grade trauma. The prevention strategies differ accordingly.
For impact injuries, there’s only so much you can do. Steel-toed boots help if you work around heavy objects. Being careful when moving furniture is obvious advice, but it’s the advice that exists. Impact injuries are accidents by nature.
Repetitive trauma is where prevention gets more interesting, because it’s almost entirely a footwear problem. Runners get subungual hematomas so frequently that “black toenail” is considered an occupational badge of honor in the running community, but it doesn’t have to be. The usual culprit is a shoe that’s slightly too short or too narrow, allowing the toes to jam forward with each stride, especially on downhills. Leaving about a thumb’s width of space between your longest toe and the end of the shoe eliminates most of this. Lacing techniques that lock the heel in place and prevent the foot from sliding forward also help.
Keeping toenails trimmed short and straight across removes another point of contact. A nail that extends past the tip of the toe is more likely to catch inside the shoe and take the brunt of impact. Moisture-wicking socks reduce friction. Some runners use toe caps or silicone sleeves on their most vulnerable toes for additional protection during long events.
Why Diabetic Feet Need Special Attention
People with diabetes face a unique set of risks with any foot injury, including something as seemingly minor as a blister under a toenail. Peripheral neuropathy, a common complication of long-standing diabetes, reduces sensation in the feet. You might develop a subungual hematoma from poorly fitting shoes and not feel it until it’s already become infected. Poor circulation, another hallmark of diabetic foot disease, means injuries heal more slowly and infections progress faster.
If you have diabetes and notice any discoloration under a toenail, treat it as something that needs professional evaluation even if it doesn’t hurt. The absence of pain in a diabetic foot is not reassuring since it may simply mean the nerves aren’t reporting the problem. Regular foot checks, either self-exams or with a podiatrist, catch these issues before they escalate. What would be a minor inconvenience for someone with healthy circulation and normal sensation can become a serious wound in a diabetic foot, and the stakes go up from there.
When a Dark Spot Under the Nail Isn’t a Blister at All
One of the trickiest aspects of a dark discoloration under the toenail is that not everything that looks like a blood blister is one. Fungal infections of the toenail can occasionally cause dark discoloration, usually more brown or greenish, that might initially be mistaken for old blood. These tend to develop gradually rather than appearing suddenly after an injury, and they’re typically accompanied by thickening, crumbling, or distortion of the nail itself.
More concerning is subungual melanoma, a rare but serious form of skin cancer that develops in the pigment-producing cells of the nail matrix. It often appears as a dark longitudinal streak running from the base of the nail toward the tip, sometimes expanding in width over time. Unlike a hematoma, it doesn’t grow out with the nail, and it may eventually cause the nail to crack or separate. Subungual melanoma is rare across all populations, but it accounts for a disproportionate share of melanoma cases in people with darker skin tones, where it is sometimes diagnosed late because it’s mistaken for trauma or a bruise.
The practical rule is straightforward: if you have a dark spot under a toenail that you can link to a specific injury, and it gradually moves toward the tip of the nail as the nail grows, it’s almost certainly a hematoma doing exactly what hematomas do. If the discoloration appeared without trauma, doesn’t move with nail growth, or keeps getting bigger over weeks, get it looked at by a dermatologist. The treatment difference between a blood blister and a melanoma is the difference between a bandage and surgery, so catching the distinction early matters enormously.