Subungual Hematoma (Black Toenail) 2026: Treatment, Drainage & Melanoma Warning

One of the more dramatic-looking foot injuries we evaluate at Balance Foot & Ankle is the black toenail — technically called a subungual hematoma. The purple-black discoloration and throbbing pressure under the nail can be alarming, especially for runners who find their toenail has mysteriously darkened after a long race. Most of the time, this is a straightforward injury that resolves on its own. But knowing when the pain warrants drainage, understanding the nail regrowth timeline, and — most critically — knowing when dark nail discoloration might not be a hematoma at all: these distinctions can make a significant difference in outcome.

What Is a Subungual Hematoma

A subungual hematoma is an accumulation of blood in the space between the nail plate and the nail bed, caused by rupture of the subungual vessels. The nail plate is essentially rigid — when blood accumulates under it, the pressure has nowhere to go. This is why subungual hematomas can be exquisitely painful: the pressure builds against the unyielding nail plate, creating the throbbing, pulsating pain characteristic of this injury.

The discoloration ranges from bright red (very fresh) to purple to black (older, clotted blood) within hours to days of injury. Over weeks, as the nail grows forward and the hematoma is carried toward the free edge, the black area migrates distally — a helpful distinguishing feature from other nail discolorations that remain stationary.

Causes: Acute Trauma vs. Repetitive Runner’s Toe

Acute Trauma

The most common cause is a direct blow to the toenail — dropping a heavy object on the toe, stubbing the toe forcefully against furniture, or having the foot stepped on. The impact crushes the soft subungual tissue against the underlying phalanx, rupturing the capillaries. Large hematomas (covering more than 50% of the nail area) from significant trauma may be associated with a distal phalanx fracture — this should be evaluated radiographically, especially if the toe is significantly swollen, deformed, or the mechanism involved high force.

Repetitive Microtrauma (Runner’s Toe / Hiker’s Toe)

Runners, hikers, and athletes in any sport involving repetitive forefoot impact commonly develop black toenails without a single acute injury. The mechanism: with each step, the longest toe (usually the second toe in patients with Morton’s toe, or the hallux) impacts the front of the shoe’s toe box. Over miles of repetitive impact, this microtrauma accumulates sufficient capillary damage to produce a hematoma. Contributing factors:

• Shoes that are too short — the most common cause; there should be ~1cm of space between the longest toe and the shoe front
• Downhill running or hiking — the foot slides forward with each step, compressing the toes against the front
• Shoes that are too wide in the toe box — excessive volume allows the foot to slide forward and toes to “hammer” against the front
• Tight lacing — can create superior compression; or loose lacing — allows heel lift and forward slide
• Morton’s toe or long second toe — a second toe longer than the hallux bears the first impact in the shoe

Treatment: When to Wait vs. When to Drain

The decision to drain (trephinate) a subungual hematoma depends on one factor: pain. Not size. Not appearance. Pain. A large black toenail that is minimally tender and doesn’t interfere with walking needs nothing but time. A small but exquisitely painful hematoma where pressure is building may warrant trephination for immediate relief.

Conservative Management (Most Cases)

1. Ice the toe immediately after injury — 15–20 minutes on, 20 minutes off for the first 24–48 hours. Ice reduces secondary bleeding and inflammation.
2. Elevate the foot above heart level for the first 24–48 hours to reduce blood pooling.
3. Take ibuprofen or naproxen for pain and anti-inflammatory effect. Acetaminophen for pain if NSAIDs are contraindicated.
4. Protect the toe with a loose, cushioned bandage. Do not compress the nail — any compression increases the pain from the built-up pressure.
5. Switch to open-toe or roomy footwear until acute pain resolves (typically 48–72 hours).
6. The nail may fall off — see the section below on what to expect.

Trephination: The Nail Drainage Procedure

Trephination creates a small hole through the nail plate to drain the accumulated blood, relieving the subungual pressure. In our clinic, this is one of the most immediately gratifying procedures we perform: patients with severe throbbing nail pain describe relief within seconds of the procedure.

How it’s done: A digital block (local anesthetic at the toe base) is administered for patient comfort, though many small hematomas can be drained with a heated wire or battery-powered cautery instrument without anesthetic — the sensation is mild pressure, not pain, when the nail plate is perforated. A single small hole (1–2mm) is made through the nail plate at the area of maximum discoloration. Blood drains immediately; the relief is typically instant. The hole is covered with antibiotic ointment and a dressing.

Timing matters: Trephination is most effective within 24–48 hours of injury, before the blood clots solidly. After 48–72 hours, the blood becomes increasingly viscous and may not drain freely even with trephination. After this window, conservative management with time is typically the only option.

Can you do this at home? We do not recommend at-home trephination. Patients attempt this with paper clips heated in flames, heated needles, or sharp objects — the risk of going through the nail plate into the nail bed (causing significant pain and potential nail bed injury) is real. Professional trephination takes 5 minutes and ensures the hole is the right depth and location.

What to Expect if the Nail Falls Off

Patients are often alarmed to discover their toenail has partially or completely detached after a subungual hematoma. This is normal and expected — the accumulated blood separates the nail plate from the nail bed, and the nail may loosen and eventually fall off or need to be gently trimmed away as it detaches. Key points about nail loss after hematoma:

• The new nail is already forming underneath — the nail matrix at the base continues to produce nail regardless of what happens to the old nail plate above
• Keep the nail bed clean and covered with antibiotic ointment and a non-adherent dressing while it’s exposed
• Do not forcibly remove a nail that’s still partially attached — let it detach naturally
• The new nail takes 6–12 months to fully grow in; it may initially look ridged, thickened, or irregular — this is normal as the new nail plate finds its path
• Occasionally the nail grows back permanently thickened or with ridges if the nail bed was significantly damaged by the injury; this sometimes requires podiatric management

Critical: Subungual Hematoma vs. Subungual Melanoma

This is the most important section of this entire guide. Subungual melanoma — a potentially life-threatening skin cancer — can appear as dark discoloration under the toenail, and it is frequently misdiagnosed as a subungual hematoma for months or years before the correct diagnosis is made. This delay in diagnosis can be fatal: subungual melanoma has a 5-year survival rate of 87% when diagnosed at Stage I but drops to 15% at Stage IV.

The clinical rule: Any dark discoloration under a toenail without a clear, documented trauma history must be evaluated by a podiatrist or dermatologist. Any discoloration that has not moved distally with nail growth after 2–3 months must be biopsied. Any dark discoloration with Hutchinson’s sign (pigment extending onto the periungual skin fold) requires urgent biopsy. In our clinic, we take an aggressive approach to nail biopsies when any diagnostic uncertainty exists — the cost of a biopsy is trivial compared to the consequence of missing a melanoma.

Runner’s Toe Prevention for Athletes

Runners who experience recurring black toenails don’t have to accept them as inevitable. The cause is almost always footwear-related, and the solutions are straightforward:

• Shoe size check: Running shoes should be one full size larger than dress shoes. Feet swell during long runs; buy shoes at the end of the day when feet are at their largest.
• Toe box clearance: Ensure 1–1.5cm (approximately a thumbnail’s width) between the longest toe and the front of the shoe when standing.
• Lacing technique: The “loop lace lock” or “heel lock” technique prevents heel slippage and forward toe impact. YouTube has excellent tutorials for this.
• Trim toenails straight across and keep them short before long runs. Long nails impact the shoe front before the pulp of the toe does.

PowerStep Pinnacle insoles provide metatarsal support that reduces forefoot slide within the shoe — keeping the foot from migrating forward into the toe box during downhill running. For runners with Morton’s toe (long second toe), a metatarsal pad positioned just proximal to the second metatarsal head reduces the disproportionate impact at that toe. Not Ideal For: patients with prescribed custom orthotics, or racing flats with minimal interior volume.

The Most Common Mistake with Subungual Hematoma

The most common mistake is treating a subungual melanoma as a hematoma for months or years because “I remember hitting my toe.” Many patients — and even some clinicians — dismiss dark nail discoloration in active patients because there’s a plausible trauma story. But subungual melanoma most commonly affects the hallux and little toe, and many patients with melanoma can recall some nail trauma in the past. The critical question is not “did I injure this nail?” but “has this discoloration moved distally with nail growth, as a hematoma must?” If the dark area is still at the base of the nail after 3 months, it cannot be a hematoma from an injury 3 months ago — nail grows outward, not inward. Biopsy is mandatory.

Warning Signs: When to Seek Urgent Evaluation

Frequently Asked Questions

Sources

1. de Berker D, Baran R. “Science of the nail apparatus.” In: Baran R, de Berker DAR, Holzberg M, eds. Baran and Dawber’s Diseases of the Nails and their Management. 4th ed. 2012.
2. Dika E, Ravaioli GM, Fanti PA, et al. “Subungual melanoma: a review of 12 cases.” Acta Derm Venereol. 2016;96(7):950-955. doi:10.2340/00015555-2373
3. Haneke E. “Important malignant and new nail tumours.” J Dtsch Dermatol Ges. 2011;9(8):636-650.
4. Rubin AI, Chen EH, Ratner D. “Basal-cell carcinoma.” N Engl J Med. 2005 [general nail anatomy review].
5. Tully AS, Trayes KP, Studdiford JS. “Evaluation of nail abnormalities.” Am Fam Physician. 2012;85(8):779-787.

Dr. Tom Biernacki, DPM

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.