Medically Reviewed | Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle, Michigan
Quick Answer:
Quick Answer: A subungual hematoma is a collection of blood beneath the toenail — caused by acute trauma (door, heavy object, stubbing) or repetitive microtrauma (runner’s black toenail, tight-fitting footwear). Small hematomas (<25–50% of nail surface) may be observed and allowed to resolve; larger, painful hematomas are treated with trephination (drilling a small hole through the nail to release pressure and blood). Nail avulsion (removal of the nail plate) is indicated when the nail is detached, for chronic ingrown management, or when underlying nail bed injury requires inspection and repair. Dr. Biernacki performs both procedures in-office at Balance Foot & Ankle PLLC.
A black or dark purple toenail after stubbing your toe, dropping something heavy on your foot, or completing a long run or hike is almost certainly a subungual hematoma — a collection of blood trapped beneath the nail plate. It’s one of the most common foot injuries Dr. Tom Biernacki treats at Balance Foot & Ankle PLLC, and it’s also one of the most satisfying to treat: releasing the pressure typically provides dramatic, immediate relief.
This page explains when a black toenail needs urgent attention, how trephination works, when nail avulsion is indicated, and what runner’s toenail is and how to prevent it.
What Is a Subungual Hematoma?
The toenail lies in a tight space between the nail plate (the hard visible nail) and the nail bed (the vascular tissue below). When trauma forces blood into this space, pressure builds rapidly with nowhere to go — producing the characteristic throbbing pain and dark discoloration that patients describe as unbearable within the first 30–60 minutes of injury.
The discoloration progresses from bright red to dark red to purple/black as the blood clots and oxidizes. The degree of pain correlates with pressure — small hematomas may be almost painless while large ones involving the majority of the nail bed are intensely throbbing.
When Does a Black Toenail Need Treatment?
Not every subungual hematoma requires draining. Indications for trephination (drainage) include:
- Hematoma involving greater than 25–50% of the nail surface area
- Significant throbbing pain — pain out of proportion to appearance
- Acute presentation within 24–48 hours of injury (blood is still liquid)
- Evidence of nail separation from the nail bed
Small, minimally painful hematomas (<25% nail surface) in an otherwise healthy nail can be observed — the blood will reabsorb over 6–12 weeks as the nail grows out. The nail may still turn black and eventually separate (onycholysis), but this is cosmetic and self-resolving.
Trephination: Draining the Hematoma
Trephination involves creating a small drainage hole through the nail plate using an electrocautery device (heated wire tip) or a hand drill (battery-powered nail trephine). The procedure is performed after the nail surface is cleaned; local anesthesia is typically not required because the nail plate has no nerve supply — only the nail bed underneath does, and the blood under pressure buffers contact with sensitive tissue in most cases.
As the hole is created, blood escapes under pressure — often dramatically — immediately relieving the throbbing pain. The drainage hole is kept open by gently expressing remaining blood, and a sterile dressing is applied. Patients routinely report the pain drops from a 9/10 to a 1/10 within seconds of drainage. The procedure takes under 5 minutes.
After trephination, the nail may still eventually separate from the nail bed as the hematoma resolves and the nail bed heals — new nail growth typically replaces it over 6–9 months for a toenail.
When Is Nail Avulsion Needed?
Nail avulsion (removal of the nail plate) is indicated when:
- The nail plate is partially or completely detached from the nail bed after trauma
- Underlying nail bed laceration requires direct inspection and repair with fine suture
- The nail is fractured or shattered and cannot be preserved
- An associated distal phalanx fracture with nail avulsion is present (often an open fracture requiring thorough irrigation)
- The nail has become chronically ingrown and the nail border requires permanent removal (partial nail avulsion with phenol matrixectomy)
Partial nail avulsion involves removing the affected nail border and applying phenol (acid) to the nail matrix to permanently prevent regrowth of that nail segment — the same procedure used for chronic ingrown toenails. Total nail avulsion removes the entire nail plate; the nail will regrow over 9–12 months (toenail) or 4–6 months (fingernail).
Runner’s Black Toenail
Distance runners, hikers, and trail runners commonly develop subungual hematomas from repetitive microtrauma — the nail repeatedly striking the toe box of the shoe with each forefoot contact over miles and hours. The 2nd toe is most commonly affected (often the longest), followed by the hallux.
Prevention focuses on proper shoe fitting: shoes should have a thumbnail’s width (12–15mm) of space between the longest toe and the front of the shoe box, particularly for downhill running or hiking where the foot slides forward. Slightly shorter nails, moisture-wicking socks to reduce sock bunching, and lacing techniques that secure the heel and prevent forward slide all reduce nail trauma. Toenail-specific products like toe guards and athletic toe tape provide additional protection for athletes prone to this problem.
Is a Black Toenail Ever Serious?
Most black toenails are straightforward traumatic hematomas. However, a dark lesion under the nail without a clear history of trauma — particularly a brown or black streak running longitudinally from the nail base — warrants urgent evaluation. Subungual melanoma (nail unit melanoma) is rare but occurs and can mimic a hematoma. It does not grow out with the nail or resolve over weeks. Any pigmented nail lesion without an obvious traumatic etiology should be examined by a physician promptly. Dr. Biernacki evaluates pigmented nail lesions and refers to dermatology for biopsy when malignancy cannot be excluded clinically.
Dr. Tom's Product Recommendations
Injinji Toe Socks — Running Compression
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Dr. Tom says: “”I got black toenails on every marathon until I switched to Injinji toe socks. No black nails at my last three races.””
Best for: Distance runners, trail runners, hikers prone to runner’s black toenail
Not ideal for: Patients with interdigital calluses or very short toes that don’t fill the toe sleeves
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Podiazole Antifungal & Nail Solution
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Applied to the nail bed after a hematoma resolves and the nail plate separates, this antifungal solution protects the vulnerable exposed nail bed and regrowing nail from opportunistic fungal infection — a common secondary complication after nail trauma.
Dr. Tom says: “”My podiatrist recommended applying this to my nail bed after my black toenail fell off. The new nail grew back completely healthy.””
Best for: Post-hematoma nail bed protection during regrowth, preventing secondary fungal nail infection
Not ideal for: Active wound care during the acute hematoma phase
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Soft gel toe cap protectors that cushion and protect the toe after nail avulsion or during recovery from a traumatic nail injury. Medical-grade silicone prevents shoe friction against the tender nail bed during regrowth.
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Best for: Post-nail avulsion nail bed protection, traumatic nail loss recovery
Not ideal for: Active nail infections — treat infection first before mechanical protection
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✅ Pros / Benefits
- Trephination provides dramatic immediate pain relief in under 5 minutes with no local anesthesia needed in most cases
- Runner’s black toenail is almost entirely preventable with proper shoe fitting and sock selection
- Nail avulsion is a definitive treatment for detached traumatic nails and chronic ingrown nails
❌ Cons / Risks
- Even after trephination, the nail typically separates over 4–8 weeks and requires 6–9 months to fully regrow
- A dark nail streak without trauma history requires urgent evaluation to rule out subungual melanoma
- Post-avulsion nail bed is vulnerable to secondary fungal infection — prophylactic antifungal application is recommended
Dr. Tom Biernacki’s Recommendation
Subungual hematomas are one of the most gratifying emergency treatments in our office because the relief is immediate and total. Patients come in with a throbbing, purple, excruciating nail and they leave 10 minutes later completely comfortable. The key decision point is identifying whether there’s an underlying nail bed laceration or fracture — because those need more than just trephination. And I always check a painless dark streak under the nail carefully for the classic history: no trauma, slowly progressing over weeks or months, not growing out. That’s the one you don’t want to miss.
— Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle
Frequently Asked Questions
Can I drain my own black toenail at home?
Home trephination is not recommended. Achieving a clean through-nail hole without burning the nail bed requires precise control of temperature (with cautery) or drill pressure. Improperly done, you can burn the sensitive nail bed, create an infection entry point, or drive bacteria into the nail bed with a contaminated tool. Professional in-office trephination takes under 5 minutes, is essentially painless, and prevents complications.
How long does it take for a nail to grow back after avulsion?
Toenails grow approximately 1–2mm per month, so a full toenail takes 9–12 months to regrow completely from the nail matrix after total avulsion. The hallux (big toenail) takes longest; smaller toenails average 6–9 months. The newly forming nail is initially soft and translucent and gradually thickens and hardens. Fingernails grow faster at 2–4mm/month, with complete regrowth in 4–6 months.
Should I remove my toenail if it’s black from running?
Not necessarily. A runner’s black toenail that is attached (not lifting from the bed) and not very painful can often be managed conservatively — allowing the nail to grow out and eventually separate on its own. If the nail is very painful (high-pressure hematoma) or the nail plate is already separating, trephination or assisted removal of the detached portion prevents ongoing friction trauma and reduces infection risk. Dr. Biernacki makes this determination at evaluation.
When should I be concerned that a dark nail might be cancer?
Seek evaluation for any dark nail streak (melanonychia) that appears without a clear injury event, has been present for more than 4–6 weeks, is progressively enlarging or darkening, extends onto the nail folds (Hutchinson’s sign), or is accompanied by nail distortion. Subungual melanoma is rare but is real — it is among the most missed diagnoses in dermatology because it’s assumed to be traumatic. Toenail melanoma most commonly involves the hallux.
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Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.
- Diagnosis and Treatment of Plantar Fasciitis (PubMed / AAFP)
- Heel Pain (APMA)
- Hallux Valgus (Bunions): Evaluation and Management (PubMed)
- Bunions (Mayo Clinic)
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