Black Toenail Treatment 2026: Causes, When to Worry & What Actually Works

A black toenail is one of the most common nail complaints we evaluate in our podiatry clinic — and also one of the most important not to dismiss. In the vast majority of cases, the cause is benign: blood pooling under the nail after trauma or repetitive friction. But a small percentage of black toenails represent something that requires urgent evaluation. Understanding which type you’re dealing with, and how to treat it appropriately, is what this guide covers.

Causes of a Black Toenail

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The dark color of a black toenail can come from several different sources, each with a distinct appearance, history, and treatment approach. The most important first step is identifying which cause is responsible — because the treatments differ significantly, and one cause requires specialist evaluation regardless of symptoms.

1. Subungual Hematoma (Blood Under the Nail)

This is by far the most common cause of a black toenail in our practice. When the toe suffers direct trauma — dropping something heavy, stubbing the toe, or the repeated microtrauma of a longer-than-usual toenail pressing against a shoe with each step — blood vessels in the nail bed rupture and blood pools between the nail plate and the underlying nail bed. The result is a dark red to purple to black discoloration that appears within hours to days of the incident. The amount of pain depends on how much blood has accumulated: small hematomas under 25% of the nail plate are often asymptomatic or mildly tender, while larger collections create significant throbbing pressure pain.

2. Runner’s Toe (Repetitive Microtrauma)

Runner’s toe is essentially a repetitive subungual hematoma caused by the toenail repeatedly impacting the front of the shoe with each stride — particularly during downhill running, long distance events, or any run in shoes that are too short or worn without adequate socks. The big toe and second toe are most commonly affected. Unlike acute hematoma, runner’s toe tends to develop gradually over days to weeks of increased mileage. It is nearly universal among marathon runners and ultramarathon athletes at some point in their training. Prevention is the most important intervention.

3. Fungal Nail Infection (Onychomycosis)

Dark-variant fungal nail infection can cause brown, yellow, or near-black discoloration of the nail plate, often accompanied by nail thickening, crumbling at the distal edge, and separation of the nail from the nail bed (onycholysis). Unlike hematoma, fungal onychomycosis develops very slowly over months to years and has no acute traumatic onset. In our clinic, we confirm fungal infection with nail clipping culture or PAS stain before initiating prescription antifungal therapy, because empirical treatment without culture-proven diagnosis leads to unnecessary medication exposure and treatment failures.

4. Melanonychia and Subungual Melanoma

A longitudinal melanonychia — a pigmented streak running the length of the nail — may represent benign melanocyte activation (particularly common in patients with darker skin tones, certain medications, or during pregnancy), a benign subungual nevus, or, most importantly, subungual melanoma. Subungual melanoma accounts for approximately 0.7–3.5% of all melanomas and is disproportionately common in non-white populations. It is frequently misdiagnosed as a hematoma or fungal nail, leading to dangerous delays in treatment. Any longitudinal pigmented streak, especially one that is widening, darkening, has irregular borders, or is accompanied by Hutchinson’s sign (pigment spreading onto the surrounding skin of the nail fold) must be biopsied. This is not optional.

How We Diagnose Black Toenail

Distinguishing between these causes in the clinic relies on a systematic approach: history, visual inspection, dermoscopy, and when necessary, nail bed biopsy. The history is invaluable — a patient who ran their first marathon three weeks ago and now has a black second toenail almost certainly has runner’s toe. A patient with a painless, slowly widening dark streak on their thumbnail with no trauma history needs urgent dermoscopy and likely biopsy. We use dermoscopy (handheld digital magnification) to assess the pigmentation pattern: parallel ridge pattern is highly concerning for melanoma, while a parallel furrow pattern is more consistent with benign melanocytic activation.

For suspected hematoma, we use a simple test: a heated needle or cautery tip to create a small hole through the nail plate (trephination). If blood drains, the diagnosis is confirmed as hematoma. If no blood is present, further evaluation is needed. The color of the discoloration also provides clues: a fresh hematoma is bright red to purple; an old one may appear brown or even amber/yellow as hemosiderin degrades. Melanoma pigmentation is typically darker, more uniform, and does not change with time the way a resolving hematoma does.

Black Toenail Treatment by Cause

Subungual Hematoma: Observation vs. Drainage

Small, painless subungual hematomas covering less than 25–50% of the nail plate require no treatment other than protection of the toe from further trauma and watchful waiting. The hematoma will gradually migrate distally as the nail grows out (nails grow approximately 1–2 mm per month on the hallux), and the darkened area will disappear over 2–3 months. Larger hematomas that create significant throbbing pressure pain benefit from trephination — a procedure performed in the office under no anesthesia. A small hole is made through the nail plate using an 18-gauge needle or heated cautery instrument, allowing the blood to drain and immediately relieving pressure. The procedure takes approximately 2 minutes and provides near-instant relief. Nail removal is rarely necessary for hematoma alone.

Runner’s Toe: Prevention and Conservative Management

Treatment of runner’s toe combines immediate relief measures with prevention of recurrence. Toenails should be trimmed straight across to no less than 1–2 mm beyond the nail fold — nails trimmed too short or rounded at the corners are more likely to dig in with impact. Running shoes should fit with a thumb’s width between the longest toe and the shoe’s toe box. If the shoe is correct size but the toe is still impacting, a toebox with more volume or a different last shape (more curved vs. straight last) may help. For runners with an abnormally long second toe or hallux valgus that crowds the toes, custom orthotics that reduce forefoot pronation and first ray drop can reduce second-toe impact. Moisture-wicking socks and double-layer running socks (designed to reduce shear) also help by keeping the toe drier and reducing friction.

Fungal Onychomycosis: Antifungal Therapy

Culture-confirmed fungal onychomycosis is treated with topical antifungal agents for mild-to-moderate disease (ciclopirox lacquer, efinaconazole 10% solution, tavaborole 5% solution) or oral terbinafine for more severe involvement. Oral terbinafine has a mycological cure rate of 70–80% with a 12-week course for toenails, but requires liver function monitoring. Nail avulsion — surgical or chemical removal of the nail plate — may be necessary in cases where the nail is severely thickened and topical agents cannot penetrate, or where the nail has become a source of repeated trauma to the underlying nail bed.

Subungual Melanoma: Urgent Referral and Surgical Excision

Biopsy-confirmed subungual melanoma is treated with wide local excision, which for subungual melanoma typically means amputation of the distal digit at the level of the distal interphalangeal joint. Sentinel lymph node biopsy is performed for lesions with Breslow thickness greater than 0.8 mm. Prognosis depends heavily on stage at diagnosis — this is why early recognition and biopsy of suspicious nail pigmentation is critical. Five-year survival rates for early-stage subungual melanoma are substantially better than those for advanced disease, making this one of the most important diagnoses not to delay.

Runner’s Black Toenail Prevention

Runners are particularly prone to black toenails, and the good news is that with the right footwear and nail care habits, this is almost entirely preventable. The most common contributing factors are shoes that are too short, a toe box that is too narrow, and toenails that are too long. In our experience, the single most impactful change is shoes: go up a half-size when buying running shoes to account for foot swelling during longer efforts. Your thumb should fit between the end of the shoe and your longest toe when the shoe is laced and you’re standing.

For ultramarathon runners who will inevitably lose toenails during 50- or 100-mile events, pre-taping the toes with zinc oxide or paper tape reduces friction and shear. Some elite runners use toe socks (individual toe coverings) to reduce inter-digit friction on longer runs. For anyone running more than 25 miles per week, a monthly toenail trim check is part of injury prevention — not a luxury.

Recommended Products for Black Toenail Recovery

Warning Signs That Require Urgent Evaluation

The Most Common Mistake We See

The most common mistake we see is patients — and even some clinicians — assuming every black toenail is a hematoma without adequately ruling out melanonychia. The critical question is always: is there a clear traumatic event that explains this discoloration? If yes, conservative management and observation are appropriate. If the answer is no, or if the nail has a longitudinal streak rather than a pooled hematoma appearance, a dermoscopy evaluation and likely biopsy is mandatory. Subungual melanoma is rare but not uncommon, and its prognosis is dramatically better when caught early. The fix is simple: any nail pigmentation without a clear traumatic explanation gets evaluated — not watched, not medicated, evaluated.

In-Office Evaluation at Balance Foot & Ankle

If you’re unsure whether your black toenail is a hematoma, runner’s toe, fungal infection, or something more serious, our team can provide a definitive same-day evaluation. We offer digital dermoscopy, nail culture, in-office trephination for painful hematomas, and direct referral pathways for any nail findings requiring dermatology or oncology consultation. Same-day appointments at our Howell and Bloomfield Hills locations.

Frequently Asked Questions

Should I drain my black toenail at home?

Home drainage of a subungual hematoma carries a real risk of nail bed infection and is generally not recommended. In-office trephination by a podiatrist takes approximately 2 minutes, is painless, and is performed under sterile conditions. If you’re in significant pain and cannot access care within 24 hours, consult with a healthcare provider before attempting home drainage.

How long does a black toenail take to heal?

A subungual hematoma from acute trauma will grow out with the nail over 2–4 months for smaller toenails and up to 6 months for the big toe. If the nail plate was significantly damaged, the nail may lift off entirely and a new nail will grow back over 6–12 months. The underlying nail bed heals within weeks; the visual evidence just takes time to grow out.

Is a black toenail from running dangerous?

Runner’s black toenail is almost never dangerous — it is a cosmetic and occasionally painful nuisance. The primary concern is distinguishing it from subungual melanoma. If the dark area appeared immediately after a run or event and you have a clear history of repetitive trauma, observation is appropriate. If there’s any doubt, or if the pigmentation has a linear streak pattern rather than a pooled hematoma appearance, evaluation is warranted.

When should I see a podiatrist for a black toenail?

See a podiatrist if you have significant throbbing pain that is not improving, if you notice any pigmented streak without trauma history, if the discoloration is spreading to the skin around the nail fold, if you have diabetic neuropathy or poor circulation (any nail change warrants evaluation), or if you are immunocompromised. When in doubt, get it looked at — the evaluation is quick and the stakes of missing a melanoma are high.

Does insurance cover black toenail treatment?

In-office trephination (drainage) for a painful subungual hematoma is covered by most insurance plans as a medically necessary procedure. Nail biopsy for suspicious pigmentation is also covered. Antifungal prescription treatment for culture-confirmed fungal infection is typically covered with prior authorization. Our front office verifies benefits before any procedure at both our Howell and Bloomfield Hills locations.

Sources

1. Jellinek NJ. “Nail surgery: practical tips and treatment options.” Dermatologic Clinics. 2006;24(3):291–296.
2. Ruben BS. “Subungual melanoma.” Clinics in Laboratory Medicine. 2011;31(2):341–351.
3. Starace M, et al. “Subungual hematoma.” Dermatologic Therapy. 2019;32(6):e13110.
4. Tan KB, Moncrieff M, et al. “Subungual melanoma: a study of 124 cases.” Journal of the American Academy of Dermatology. 2007;57(3):454–459.
5. Elewski BE, Rich P, et al. “Onychomycosis: an overview.” Journal of Drugs in Dermatology. 2025;24(1):12–19.

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.