✅ Medically reviewed by Dr. Thomas Biernacki, DPM — Board-Certified Podiatrist · Last updated April 6, 2026

Finding a dark or black spot under your toenail can be alarming. Your mind might jump to worst-case scenarios — and while it’s important to take any new toenail discoloration seriously, the vast majority of cases have benign, treatable causes. At Balance Foot & Ankle, we evaluate dark toenail spots every week and can quickly determine whether yours needs monitoring, treatment, or a biopsy.

Common Causes of Black Spots Under Toenails

Updated April 2026. A black spot under the toenail is most commonly a subungual hematoma (blood blister from trauma) but can rarely indicate subungual melanoma. Most trauma-related spots grow out with the nail over 6-9 months. See a podiatrist immediately if the dark spot appeared without injury, has irregular borders, or is expanding.

Dark discoloration under a toenail can range from a harmless bruise to a sign of something more serious. The color, pattern, location, and history of the spot all help us determine its cause. Here are the most common reasons you might see a black or dark spot under your nail.

Subungual Hematoma (Bruised Toenail)

The most common cause of a black toenail is a subungual hematoma — a collection of blood between the nail plate and nail bed. This typically happens after direct trauma (stubbing your toe, dropping something on it) or repetitive microtrauma (running in shoes that are too small, hiking downhill). Runners are especially prone, which is why it’s sometimes called “runner’s toe.”

A subungual hematoma usually appears as a dark reddish-purple to black spot that doesn’t extend to the nail edges. You may recall the specific injury, or the discoloration may develop gradually from repetitive friction. As the nail grows out (roughly 1mm per month for toenails), the spot moves with it toward the tip — this is a reassuring sign that it’s blood-related rather than a growth in the nail bed.

Small hematomas resolve on their own as the nail grows out over 6–12 months. Large, painful hematomas may need drainage (trephination) — a quick, painless in-office procedure where a small hole is created in the nail to release the trapped blood and relieve pressure.

Toenail Fungus

While most toenail fungus causes yellowing or white discoloration, certain fungal species — particularly molds and dermatophytes — can produce dark brown or black pigmentation. Fungal melanonychia is more common in darker skin tones and may present as a diffuse dark discoloration rather than a discrete spot.

Other clues that fungus is the cause include nail thickening, crumbling, lifting from the nail bed, and an unpleasant odor. A fungal culture or nail biopsy can confirm the diagnosis. Unlike a hematoma, fungal discoloration doesn’t move with nail growth — it tends to stay in place or spread. Treatment includes topical antifungals, oral medications, or laser therapy depending on severity. Learn more about professional toenail fungus treatment.

Subungual Melanoma

Subungual melanoma is a rare but serious form of skin cancer that originates in the nail matrix (the tissue beneath the base of the nail). It accounts for about 0.7–3.5% of all melanomas but has a poorer prognosis than cutaneous melanoma because it’s often diagnosed late. It’s more prevalent in individuals with darker skin tones and typically affects the big toe or thumb.

The ABCDEF mnemonic helps identify concerning features: Age (peak 50–70 years), Brown-to-black band wider than 3mm, Change in size or color, Digit most commonly affected (big toe, thumb), Extension of pigment onto the surrounding skin (Hutchinson sign), and Family or personal history of melanoma. Any dark streak that extends from the nail matrix to the tip, especially if it widens or bleeds to surrounding skin, warrants urgent evaluation.

Other Causes

Beyond subungual hematoma, a black spot under the toenail may indicate melanoma (the most serious possibility), a benign nevus of the nail matrix, bacterial infection producing dark pigment, or a dark streak present from birth. Any black line or spot under a toenail that cannot be directly linked to a specific recent trauma must be promptly evaluated by a podiatrist or dermatologist.

Bacterial infection: Pseudomonas bacteria can colonize the space between a lifted nail and the nail bed, producing a characteristic green-black discoloration sometimes called “green nail syndrome.” This is treated with topical antibiotics and keeping the area dry.

Medications: Certain drugs including chemotherapy agents, antimalarials (hydroxychloroquine), and some antibiotics can cause nail hyperpigmentation. This typically affects multiple nails and resolves after discontinuing the medication.

Ethnic melanonychia: Longitudinal brown or black streaks are a normal finding in up to 77% of African Americans over age 50 and are common in other darker-skinned populations. These typically affect multiple nails and remain stable over time. However, any change in a pre-existing streak still warrants evaluation.

When to Worry: Warning Signs

Most black spots under toenails are harmless, but you should see a podiatrist if the spot appeared without trauma, if it’s growing or changing shape, if pigment is spreading to the skin around the nail, if the nail is crumbling or destroyed, or if you’re over 50 and notice a new single-nail dark band. Early detection of subungual melanoma dramatically improves outcomes — the 5-year survival rate drops from over 80% for Stage I to under 20% for Stage IV.

How a Podiatrist Diagnoses Dark Toenail Spots

At Balance Foot & Ankle, we use a systematic approach to evaluate dark toenail spots. This begins with a detailed history (trauma, onset, progression, medications) and visual examination under magnification. Dermoscopy — a specialized handheld device that visualizes the nail structures at 10x magnification — allows us to distinguish between blood, fungal pigment, and melanocytic features.

When melanoma is suspected, a nail matrix biopsy is the gold standard. This involves removing a small section of the nail and underlying tissue for pathological examination. We also perform fungal cultures when infection is suspected, and may order X-rays if there’s concern about bone involvement beneath the nail.

Treatment Options

Treatment depends entirely on the cause. A painful subungual hematoma is drained by creating a small hole through the nail to release pressure, providing immediate relief. Fungal or bacterial infections require antifungal or antibiotic therapy. A suspected melanoma requires urgent biopsy and oncology referral — this is never a condition to watch and wait on.

Subungual hematoma: Small hematomas need no treatment beyond monitoring. Large or painful ones can be drained with nail trephination for immediate relief. The discoloration grows out naturally over 6–12 months.

Fungal infection: Treatment depends on severity — mild cases may respond to topical antifungals (ciclopirox, efinaconazole), while moderate to severe cases require oral antifungal medication (terbinafine) for 3 months. Laser therapy is an effective adjunct treatment. See our complete guide to treating toenail fungus.

Subungual melanoma: Treatment involves surgical excision with appropriate margins, typically including amputation of the affected toe tip. Early-stage melanoma has excellent outcomes. Advanced cases may require sentinel lymph node biopsy and systemic therapy. Our team provides prompt referral to dermatology or oncology when melanoma is confirmed.

In-Office Treatment at Balance Foot & Ankle

If home care isn’t resolving your your foot or ankle concern, a visit with a board-certified podiatrist is the fastest path to accurate diagnosis and a personalized plan. At Balance Foot & Ankle Specialists, Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin offer same-day and next-day appointments at both our Howell and Bloomfield Hills offices. We perform on-site diagnostic ultrasound, digital X-ray, conservative care, advanced regenerative treatments, and minimally invasive surgery when indicated.

Call (810) 206-1402 or request an appointment online. Most insurance plans accepted, including Medicare, Blue Cross Blue Shield, Aetna, Cigna, and United Healthcare.

Frequently Asked Questions

How can I tell if a black spot under my toenail is cancer?

The key differentiators are: melanoma typically presents as a dark longitudinal streak (not a round spot), widens over time, and may extend pigment onto the surrounding skin (Hutchinson sign). A hematoma, by contrast, is usually round, moves with nail growth, and has a clear trauma history. When in doubt, always get a professional evaluation — dermoscopy and biopsy provide a definitive answer.

Will a black toenail fall off?

A large subungual hematoma (covering more than 25–50% of the nail) can cause the nail plate to separate from the nail bed, eventually leading to nail loss. The nail typically regrows over 9–18 months. If the nail is loosening, keeping it trimmed and clean prevents catching and tearing. A new nail will grow from the matrix beneath.

How long does a bruised toenail take to go away?

Toenails grow approximately 1mm per month — much slower than fingernails. A bruise at the base of the nail may take 9–12 months to fully grow out. The discoloration will gradually move toward the tip of the nail as new, healthy nail grows behind it. If the dark spot doesn’t move with growth over 2–3 months, it should be evaluated to rule out other causes.

Should I see a doctor for a black toenail?

Yes, you should see a podiatrist if the dark spot appeared without trauma, is changing in size or shape, affects only one nail, is accompanied by pain or nail destruction, or if you’re over 50. Even if it’s likely a hematoma, getting a professional confirmation gives you peace of mind and catches the rare cases that need treatment.

The Bottom Line

A black spot under your toenail is usually nothing to panic about — most cases are simple subungual hematomas from trauma or repetitive friction. However, because subungual melanoma can mimic a bruise and early detection saves lives, any unexplained or changing dark spot deserves professional evaluation. At Balance Foot & Ankle, we can typically determine the cause during a single office visit using dermoscopy and clinical examination, giving you clarity and a clear treatment path.

Clinical References

1. Levit EK, Kagen MH, Scher RK, et al. The ABC rule for clinical detection of subungual melanoma. Journal of the American Academy of Dermatology. 2000;42(2):269-274.
2. Braun RP, Baran R, Le Gal FA, et al. Diagnosis and management of nail pigmentations. Journal of the American Academy of Dermatology. 2007;56(5):835-847.
3. Haneke E. Ungual melanoma—controversies in diagnosis and treatment. Dermatologic Therapy. 2012;25(6):510-524.

Most Common Mistake We See

The most common mistake we see is: Waiting too long before seeking care. Fix: any foot pain lasting more than 4 weeks, or any sudden severe symptom, deserves a professional evaluation rather than more rest.

Warning Signs That Need Same-Day Care