Black Spot Under Toenail 2026: Causes & Treatment

You look down and notice a dark spot — black, dark brown, or deep purple — appearing under your toenail. Your first instinct might be to dismiss it as a bruise from that stubbed toe last week. And 90% of the time, you’d be right. But a small percentage of black spots under toenails are something that cannot be ignored.

Subungual melanoma — melanoma developing under a nail — accounts for up to 4% of all melanoma cases in lighter-skinned individuals and a significantly higher proportion in darker-skinned people. It is frequently misidentified as a bruise for months or years before diagnosis. Early detection makes an enormous difference in outcomes.

This guide will give you the knowledge to tell them apart — and to know exactly when to stop waiting and see a podiatrist.

6 Causes of a Black Spot Under the Toenail

1. Subungual Hematoma (Most Common — Usually Harmless)

What it is: Blood pooling under the nail plate after trauma to the toenail. When a toe is stubbed, something heavy drops on it, or the nail is subjected to repeated microtrauma (runner’s toe), small blood vessels in the nail bed rupture. Blood collects in the confined space under the nail and appears as a dark — often black, dark red, or purple — discoloration.

What it looks like: Typically appears within hours of injury as a rapidly expanding dark area. May cover a small portion of the nail or the entire nail bed. In acute injury, there’s usually significant pain and throbbing pressure as blood accumulates. Older hematomas lose their red color and turn brown or black as the hemoglobin breaks down.

Key distinguishing feature: It moves. A subungual hematoma is within the nail plate or between the nail and nail bed — as the nail grows forward, the dark spot advances toward the tip of the nail. Over 3–6 months for most toenails (9–12 months for the big toe), the dark area grows completely out to the free edge where it is trimmed off.

Treatment: Small hematomas — less than 25% of the nail — require no treatment beyond pain management with ice and elevation. Large, painful hematomas can be drained by a podiatrist (trephination) within 24–48 hours of injury to relieve pressure and reduce pain. This simple procedure takes about 2 minutes.

2. Subungual Melanoma (Must Rule Out)

What it is: Melanoma (skin cancer) developing from melanocytes in the nail matrix — the growth cells at the base of the nail. Subungual melanoma presents as a pigmented band or spot under the nail. It is rare, but its consequences when missed are severe — subungual melanoma has a significantly worse prognosis than skin melanoma due to frequent late diagnosis.

Who is at risk: Subungual melanoma affects all skin tones, but its relative proportion is higher in darker-skinned individuals (African American, Hispanic, Asian populations) — accounting for up to 20–30% of melanomas in these groups, compared to 1–3% in lighter-skinned individuals. It most commonly affects the thumb or big toenail.

What distinguishes it: It does NOT move with nail growth. It originates in the nail matrix and remains in position regardless of how long you wait. Additional warning signs are covered in the ABCDEF rule section below.

3. Splinter Hemorrhages

What it is: Tiny longitudinal (lengthwise) streaks of dark red or brown running parallel to the nail from base to tip, caused by small broken capillaries in the nail bed. These look like tiny splinters trapped under the nail — hence the name.

Common causes: Minor trauma is the most common cause of isolated splinter hemorrhages. However, multiple splinter hemorrhages across several nails simultaneously — particularly when accompanied by symptoms like fever, joint pain, or unusual fatigue — can be a sign of systemic conditions including infective endocarditis, vasculitis, lupus, or certain medication effects.

Isolated splinter hemorrhages in an active person who works with their hands or plays sports are almost always traumatic and benign. Multiple spontaneous splinter hemorrhages warrant a medical workup.

4. Toenail Fungal Infection

What it is: While most nail fungus causes yellow, white, or brown discoloration, some fungal species — particularly Aspergillus and certain mold infections — produce dark green, brown, or black pigmentation. Pseudomonas bacterial colonization (which can co-occur with fungal infection) produces a characteristic blue-green to black color from the pyocyanin pigment it produces.

What it looks like: Dark discoloration accompanied by nail thickening, crumbling, or a foul odor. Unlike traumatic hematoma, there’s usually no recalled injury. The nail may appear greenish-black rather than pure black. The nail is almost always dystrophic (abnormal texture, not just color).

5. Subungual Nevus (Mole Under the Nail)

What it is: A benign melanocytic lesion (mole) in the nail matrix. These appear as longitudinal melanonychia — a brown to black vertical band running from the nail base to the tip. Unlike a hematoma, the band grows with the nail from the matrix forward. Unlike melanoma, these bands typically have uniform color, regular borders, and have been present and stable for years.

All subungual nevi require monitoring. Any change in width, color uniformity, or appearance warrants biopsy to rule out early malignant transformation.

6. Subungual Exostosis or Other Benign Growth

What it is: Occasionally, a benign bony growth (exostosis) under the nail pushes upward against the nail plate, causing pressure and eventually disrupting nail bed vasculature, leading to dark discoloration. This is less common than hematoma but creates a different clinical picture — the dark area is typically focal, over the area of bony prominence, and may cause visible nail deformity.

Hematoma vs. Melanoma: How to Tell the Difference

This is the essential clinical question. Most black spots are hematomas. Some are not. Here’s what separates them:

The ABCDEF Rule for Nail Melanoma

Dermatologists and podiatrists use the ABCDEF mnemonic to evaluate suspicious nail pigmentation:

A — Age and race: Subungual melanoma peaks in the 5th to 7th decade of life. It is proportionally more common in African American, Hispanic, and Asian patients.

B — Band characteristics: Width greater than 3mm, irregular borders, or multiple shades of brown/black within the same band are concerning. A uniform, narrow band in a young person is less worrisome.

C — Change: Any recent change in a nail pigment band — wider, darker, more irregular — requires evaluation within weeks, not months.

D — Digit involvement: Melanoma most commonly affects the thumb or big toenail. A single digit affected (especially the dominant thumb or hallux) is more concerning than bilateral or multi-digit involvement (which more often indicates benign causes).

E — Extension (Hutchinson’s sign): Pigment spreading from the nail onto the surrounding cuticle or skin fold is a major warning sign. This extension — called Hutchinson’s sign — indicates the pigment is coming from active melanocytes growing beyond the nail unit, which is characteristic of melanoma. A pseudo-Hutchinson’s sign (where visible pigment through a transparent cuticle mimics this) is a benign variant that experienced podiatrists can identify.

F — Family history: Personal or family history of melanoma increases concern for nail melanoma.

Black Spot Under Toenail Not Going Away — What This Means

If a black spot under your toenail is not moving with nail growth after 2–3 months — meaning the dark area stays at the same location rather than advancing toward the nail tip — this is a significant red flag.

A hematoma, by definition, is trapped blood between the nail plate and nail bed. As the nail grows forward (approximately 1.5mm per month for toenails), the trapped blood moves with it. A spot that doesn’t move is not a hematoma — it’s either a pigmented lesion originating in the nail matrix or nail bed (melanocytic nevus or melanoma) or another structural cause.

The practical test: take a clear photo of the nail today, marking the position of the dark area relative to the cuticle and nail tip. Repeat in 6–8 weeks. Has the dark area moved forward relative to the cuticle? If yes, it’s almost certainly a hematoma. If it’s in the same position relative to the cuticle — not growing out — see a podiatrist the same week for dermoscopic evaluation.

Warning Signs: See a Podiatrist Within the Week

I want to be direct with my patients about this: subungual melanoma is diagnosed late more than almost any other melanoma. People assume it’s a bruise, wait a year, and by the time they see a doctor, the melanoma has advanced. The difference between stage I and stage III subungual melanoma is enormous in terms of outcomes. Please don’t wait.

How Podiatrists Diagnose and Treat It

Dermoscopy: The first step. A handheld dermoscope (10-20x magnification with polarized light) reveals nail plate characteristics invisible to the naked eye — the pattern, color distribution, and border characteristics of nail pigmentation. This is now standard of care for evaluating nail discoloration and is available at our Michigan offices.

Photo documentation and monitoring: For lesions that are concerning but not immediately alarming, we photograph with a scale reference and schedule a 6–8 week follow-up. Any change accelerates the timeline to biopsy.

Nail biopsy: When dermoscopy reveals concerning features — or when a spot fails the movement test — nail matrix biopsy is performed. This is a minor outpatient procedure under local anesthesia. The biopsy sample is sent to dermatopathology for definitive diagnosis.

Hematoma drainage: For large, acute, painful hematomas — if seen within 24–48 hours of injury — we can drain the collected blood to relieve pressure and reduce pain immediately. This also confirms the diagnosis: drained blood confirms hematoma.

Surgical referral for melanoma: Confirmed subungual melanoma requires surgical excision, typically involving amputation of the distal phalanx (the tip of the toe). We coordinate immediately with surgical oncology when the diagnosis is confirmed.

Frequently Asked Questions

Is a black spot under the toenail always serious?

No — the overwhelming majority (approximately 90%+) of black toenail spots are subungual hematomas from trauma, which are completely benign and resolve without treatment. The challenge is identifying the minority that are not. The most reliable indicator is movement: a hematoma advances toward the nail tip as the nail grows; a melanocytic lesion stays fixed at its origin. A spot that isn’t moving after 6–8 weeks warrants professional evaluation regardless of whether you remember an injury.

How do I know if my black toenail is melanoma?

You cannot definitively determine this at home — dermoscopy and potentially biopsy are required for certainty. However, the features most associated with melanoma are: no recalled injury before the spot appeared, the spot doesn’t advance toward the nail tip over 1–2 months, pigment spreading onto surrounding skin (Hutchinson’s sign), irregular or multiple colors within the spot, width greater than 3mm, and any recent change in size or color. If several of these apply to your situation, see a podiatrist within days.

How long does a black spot under the toenail last from an injury?

A traumatic subungual hematoma lasts as long as it takes the nail to grow out past the injured area. For the big toenail, this is typically 9–18 months for the dark area to completely grow out to the nail tip where it’s trimmed off. For smaller toenails, 4–8 months is typical. The dark area changes color over time — bright red turns dark red, then brown, then black as hemoglobin breaks down. All of this is normal. What’s not normal is the spot staying in the same position rather than advancing forward.

Should I drain a black spot under my toenail at home?

No — do not attempt to drain a subungual hematoma at home with a needle, pin, or any sharp object. The risk of introducing bacteria into the nail bed causing serious infection far outweighs the benefit for most small hematomas. Large, extremely painful acute hematomas (more than 25–50% of the nail, within 24–48 hours of injury) can be drained — but this should be performed by a podiatrist using sterile technique. Small hematomas simply don’t need drainage and will resolve on their own.

Can toenail fungus look black?

Yes, though this is uncommon. Standard dermatophyte fungal infections (the most common type) produce yellow, white, or brown discoloration. However, infections with certain mold species — including Aspergillus niger — and Pseudomonas bacterial colonization (often occurring alongside fungal infections) can produce distinctly dark green, brown, or black discoloration. Fungal-related black discoloration is almost always accompanied by nail thickening, crumbling texture, and often a foul odor — distinguishing features absent from traumatic hematoma.