Medically reviewed by Dr. Tom Biernacki, DPM
Board-certified podiatric surgeon | Balance Foot & Ankle, Howell & Bloomfield Township, MI
Last reviewed: May 2026
The most important clinical decision with Black Spot on Foot: 9 Causes, When It’s Serious & When to See a Doctor isn’t which treatment to choose — it’s identifying which subtype you have first. Our podiatrists see patients treated for the wrong subtype for months before the correct diagnosis leads to full resolution. Call (810) 206-1402 — expert podiatric care across Michigan.
A black spot on the foot can range from completely harmless (bruising, dried blood) to serious (melanoma). The appearance, location, duration, and associated symptoms help narrow the cause. At Balance Foot & Ankle, our podiatrists evaluate suspicious foot lesions in Howell and Bloomfield Township, MI.
Black Spot on Foot — Causes Comparison Table
| Cause | Appearance | Location | Painful? | Action |
|---|---|---|---|---|
| Subungual hematoma (under toenail) | Dark maroon/black beneath nail; well-defined border | Under toenail, often from trauma or ill-fitting shoes | Throbbing initially; resolves | Self-limiting; see podiatrist if large or not resolving |
| Plantar wart (wart with black dots) | Flesh-colored with black pinpoints (thrombosed capillaries); interrupts skin lines | Plantar surface — weight-bearing areas | Painful with direct pressure; side pinch less painful | OTC salicylic acid; podiatry if persistent |
| Melanoma (acral lentiginous) | Irregular borders; variegated color; flat or raised; >6mm; may appear under nail | Sole, heel, under nail — often in areas not sun-exposed | Painless early; may bleed or ulcerate | URGENT — podiatry or dermatology biopsy immediately |
| Talon noir (calcaneal petechiae) | Group of black/brown dots or smudge at the heel; no skin line disruption | Posterior heel; lateral heel | No | Benign; seen in athletes; clears with gentle debridement |
| Bruise / ecchymosis | Blue-black spreading bruise; fades through yellow-green over days | Any; often dorsal or lateral after trauma | Tender initially | RICE; see doctor if not resolving in 2–3 weeks or suspect fracture |
| Gangrene | Black, dry, shrunken tissue (dry gangrene); wet gangrene: black + odor + pus | Toe tips and edges; forefoot in ischemia | May be painless due to neuropathy | EMERGENCY — vascular surgery immediately |
| Dermatofibroma | Firm nodule; brown-black; dimples inward when pinched | Dorsal foot or ankle; less common on sole | No (may be mildly tender) | Biopsy if uncertain; benign |
| Blue nevus (mole) | Blue-black, well-defined, uniform color; present for years | Anywhere | No | Biopsy if changing; otherwise monitor with ABCDE criteria |
| Diabetic foot eschar | Black or dark brown crust over pressure area; may have surrounding redness | Heel, lateral border — pressure points | Painless due to neuropathy | URGENT podiatry — unroofing and wound care needed |
ABCDE Rule — Apply to Any Dark Spot
| Letter | Stands For | Warning Sign |
|---|---|---|
| A | Asymmetry | One half does not mirror the other |
| B | Border | Irregular, ragged, or notched edges |
| C | Color | Varied — mixtures of brown, black, red, white, or blue |
| D | Diameter | Greater than 6mm (pencil eraser) |
| E | Evolution | Any change in size, shape, color, or new bleeding |
Acral Lentiginous Melanoma — The Hidden Danger
Acral lentiginous melanoma (ALM) is the most common melanoma type in dark-skinned individuals and occurs on the soles, palms, and under nails — areas rarely examined and not exposed to UV. It is frequently diagnosed late because patients assume sun-protected areas cannot develop melanoma. It accounts for approximately 5% of all melanomas but carries a worse prognosis due to delayed diagnosis.
- Pharmaceutical antiseptic skin cleanser
- Safe for a child to use, though parents should practice discretion and always supervise use
- Shown through dermatological testing to be very mild on user skin
Hutchinson’s sign — dark pigment extending from under a toenail onto the nail fold skin — is a hallmark of subungual melanoma and requires immediate biopsy.
When to Get a Black Spot Evaluated Immediately
- Black spot that appeared without trauma or is growing
- Black tissue on a diabetic foot (especially heel) — may be eschar or gangrene
- Black discoloration spreading up from a toe tip (gangrene suspect)
- Hutchinson’s sign — pigment extending from nail onto surrounding skin
- Any lesion that bleeds spontaneously or won’t heal
Don’t wait on a suspicious foot lesion. Balance Foot & Ankle provides same-week evaluation in Howell (4330 E Grand River Ave) and Bloomfield Township (43494 Woodward Ave #208). Call (810) 206-1402.
American Academy of Dermatology. Melanoma warning signs and images. AAD.org.
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Doctor Answer
What causes a black spot on the foot and when is it serious?
A black spot on the foot can have several causes ranging from benign to life-threatening. Subungual hematoma (blood under the nail) from trauma is common and grows out with the nail. Melanoma presenting as an irregular dark spot — particularly on the sole or under a nail — is the most critical concern and requires urgent evaluation. Plantar warts may have black dots from thrombosed capillaries. Talon noir is superficial black hemorrhage from shear forces in athletes. I evaluate any unexplained black spot with dermoscopy and biopsy when melanoma cannot be confidently excluded.
Dr. Tom Biernacki, DPM is a board-certified foot & ankle surgeon (ABFAS & ABPM) 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 made him one of the most-followed foot & ankle educators on YouTube.