Subungual Hematoma (Black Toenail) 2026 | DPM

Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Hills, MI. Last updated April 2026.

A dark spot under a toenail is common — and usually the result of a subungual hematoma (blood blister beneath the nail) from trauma. Most of the time there’s no cause for alarm. However, a subset of dark nail discolorations represent subungual melanoma — an aggressive form of melanoma that is frequently diagnosed at a late stage because it is dismissed as a bruise. Knowing the difference can be life-saving.

Subungual Hematoma: The Common Cause

A subungual hematoma is a collection of blood beneath the nail plate from disrupted capillaries in the nail bed, typically caused by:

• Acute trauma: stubbing a toe, dropping a heavy object, sports injury
• Repetitive microtrauma: runners whose toes repetitively impact the shoe toe box (runner’s toenail / “black toenail”)
• Ill-fitting footwear causing chronic nail bed pressure

Acute subungual hematomas are painful immediately after trauma — the pressure of blood accumulating under the nail creates intense throbbing pain. The dark discoloration (deep red to purple-black) appears within hours of the injury.

Treatment: Small hematomas (less than 50% of nail surface area) without associated nail fracture can be left to grow out naturally. Large, painful hematomas may be drained by trephination — creating a small hole through the nail plate with a heated cautery device or drill to release the blood and relieve pressure. This is a simple, office-based procedure. Subungual hematomas grow out with the nail over 6–12 months.

Subungual Melanoma: The Rare but Important Diagnosis

Subungual melanoma is a form of acral lentiginous melanoma — a melanoma subtype that develops in areas without sun exposure (palms, soles, nail units). It accounts for approximately 1–3% of all melanomas in Caucasians but is disproportionately common in Asian, African American, and Hispanic populations (up to 30–40% of melanomas in these groups). The great toenail is the most common site.

Distinguishing Features: The ABCDEs of Nail Melanoma

The following features should prompt immediate dermatology or podiatry evaluation:

• A — Age/Race: African American, Asian, or Hispanic patient; age 50–70 years
• B — Brown-Black Band: A longitudinal melanonychia (brown to black vertical streak running the full length of the nail)
• C — Change: Streak that is darkening, widening, or developing irregular borders over time
• D — Digit involved: Thumb or great toe (highest incidence sites for subungual melanoma)
• E — Extension: Hutchinson’s sign — pigmentation extending from under the nail onto the surrounding skin (proximal or lateral nail fold). This is a major red flag for melanoma.
• Single nail: Melanoma typically affects a single nail; benign longitudinal melanonychia from medications, systemic conditions, or nail matrix nevi often affects multiple nails

When Hematoma Can Be Confused with Melanoma

A round, discrete dark spot that moves distally as the nail grows out over weeks to months is consistent with a resolving hematoma. A streak that does NOT move with nail growth and persists or expands over months requires biopsy evaluation. Any nail discoloration with no clear traumatic history warrants evaluation — patients often attribute nail changes to forgotten injuries, delaying diagnosis.

What to Do

Any dark nail discoloration with Hutchinson’s sign, any non-resolving stripe without clear trauma, or any dark streak in a patient from a higher-risk demographic should be promptly evaluated by a podiatrist or dermatologist. Nail matrix biopsy is the definitive diagnostic step. Early-stage subungual melanoma confined to the nail unit is potentially curable with surgical excision; advanced lesions carry poor prognosis.

Dark Spot Under Toenail — When to Worry

A dark spot under your toenail could be a harmless bruise (subungual hematoma) or something that needs prompt evaluation. Our podiatrists help you determine whether your discolored nail needs monitoring, drainage, or biopsy to rule out subungual melanoma.

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Clinical References

1. Baran R, Kechijian P. Longitudinal melanonychia (melanonychia striata): diagnosis and management. Journal of the American Academy of Dermatology. 1989;21(6):1165-1175.
2. Thai KE, et al. Subungual melanoma: a clinical and pathological review. Australasian Journal of Dermatology. 2001;42(2):71-81.
3. Braun RP, et al. Dermoscopy of the nail. Dermatologic Clinics. 2006;24(3):349-357.

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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.