A black spot on a toe is most often a subungual hematoma, which is a pocket of blood trapped beneath the toenail after some kind of impact or pressure. But the list of possible causes is longer than most people expect, ranging from fungal infections and friction injuries to normal pigment variations and, rarely, melanoma. Because some of these causes are harmless and others demand prompt medical attention, understanding what sets them apart matters more than the spot itself.
Subungual Hematoma
The single most common reason for a dark spot under a toenail is a subungual hematoma. It happens when blood collects beneath the nail plate after an injury. Stubbing your toe, dropping something heavy on your foot, or wearing shoes that are too tight during a long run can all cause it. The blood pools under the nail and shows through as a dark red, purple, or black spot that stays put when you press on the nail.1PubMed Central. Subungual Hematoma: Insights From a Clinical Case Study
These spots can be quite painful at first because the pressure builds in a tight space between the nail and the nail bed. If the pressure is significant, a doctor can relieve it by making a small hole in the nail to let the blood drain, which typically brings fast relief.2Clinics in Podiatric Medicine and Surgery. Three Select Subungual Pathologies: Subungual Exostosis, Subungual Osteochondroma, and Subungual Hematoma A minor hematoma will usually grow out with the nail over weeks to months without any treatment. The key feature that identifies it: the discolored area moves toward the tip of the toe as the nail grows, and it does not expand or change shape on its own.
Not every subungual hematoma comes from an obvious injury. Tight or narrow shoes, repetitive pressure from walking or running, and even certain medications or systemic conditions can trigger bleeding under the nail without a single memorable impact event.2Clinics in Podiatric Medicine and Surgery. Three Select Subungual Pathologies: Subungual Exostosis, Subungual Osteochondroma, and Subungual Hematoma This is why people sometimes notice a black toenail and have no idea how it got there.
Talon Noir and Sports-Related Spots
If the black spot is on the skin of your toe rather than under the nail, one possibility is talon noir, sometimes called “black heel” even though it can appear on the toes and forefoot as well. It is caused by tiny hemorrhages within the outermost layers of skin, triggered by shearing forces from sudden stops, pivots, or repetitive friction. Basketball players, tennis players, rock climbers, and distance runners are especially prone to it.3PubMed Central. Talon Noir: A Case Report and Literature Review
What makes talon noir distinctive is that the dark spots are superficial. If you gently pare the top layer of skin, you’ll see the pigment comes away with it, because the blood is sitting right in the epidermis. The spots are painless, flat, and tend to appear in clusters of small dark specks rather than as a single solid area. They resolve on their own once the offending activity stops, and they are completely benign. The importance of recognizing talon noir is that it can look alarmingly like melanoma at a glance, leading to unnecessary anxiety or even biopsies.
Fungal Infections That Turn Nails Dark
Most people associate fungal nail infections with thick, crumbly, yellowish nails, and that is the most common presentation. But certain groups of fungi produce melanin or melanin-like pigments in their cell walls, and when these colonize a toenail the discoloration can be dark brown to black rather than the expected yellow-white. These fungi belong to a category called dematiaceous molds, and they account for a meaningful share of non-dermatophyte nail infections.4PubMed Central. Onychomycosis caused by dematiaceous fungi: A four-year study on agricultural workers of Assam, India
A darkened nail from fungal infection will usually show additional changes over time: thickening, lifting of the nail from the bed, crumbling at the edges, or debris collecting underneath. The color change is often patchy or streaky rather than a single discrete spot. A lab culture or clipping analysis can confirm the diagnosis, and treatment is the same as for other fungal nail infections, typically a course of oral antifungal medication. Over-the-counter topical antifungals sometimes help with mild cases, but dark-pigmented fungal infections tend to be deeper in the nail plate and often need systemic treatment.
Bacterial Infections and Green-Black Nails
A bacterial cause worth knowing about is Pseudomonas aeruginosa, the bug behind “green nail syndrome.” Pseudomonas thrives in moist environments and colonizes nails that are already damaged, lifted, or constantly exposed to water. While the classic color is green, the discoloration can range from greenish-yellow through greenish-brown to greenish-black, which is why some people describe it as a black spot.5PubMed Central. Chloronychia: green nail syndrome caused by Pseudomonas aeruginosa in elderly persons
Green nail syndrome tends to show up in people who frequently soak their hands or feet, or in older adults whose nails have become more brittle and separated from the nail bed. The giveaway is often the slightly green hue when you look closely in good lighting, along with onycholysis (the nail pulling away from the bed at the edges). An oral antibiotic such as ciprofloxacin is typically prescribed. Keeping the area dry and trimming back the separated nail helps prevent recurrence.
Tinea Nigra
Tinea nigra is an uncommon but under-recognized superficial fungal infection caused by the yeast-like organism Hortaea werneckii. It produces brown to black flat patches on the palms or soles, and it can extend onto the toes. The patches are painless, not raised, and often have well-defined borders.6PubMed Central. Interdigital Tinea Nigra The organism enters through tiny breaks in the skin and produces a melanin-like substance as it grows, giving the spot its dark color.7International Journal of Medical Science and Clinical Research Studies. Tinea Nigra: A Diagnostic Challenge – Hortaea Werneckii Infection Mimicking Acral Melanoma
Tinea nigra is most common in tropical and subtropical climates but occasionally appears elsewhere. The lesions are flat, not elevated, and may have fine scaling on close inspection.8PubMed Central. Tinea nigra by Hortaea werneckii, a report of 22 cases from Mexico The real clinical problem is that tinea nigra closely mimics melanoma, leading to unnecessary excisional biopsies. A simple scraping examined under a microscope reveals the pigmented fungal elements and confirms the diagnosis, and topical antifungal treatment clears it up quickly.
Plantar Warts and Dark Dots
Plantar warts caused by the human papillomavirus can develop on the toes and the bottom of the foot. They often contain tiny dark dots that people describe as “seeds.” Those dots are actually thrombosed (clotted) capillaries within the wart, not seeds at all. Under magnification, most plantar warts show dotted blood vessels along with a yellowish-brown background.9Skin Research and Technology / Wiley Online Library. Clinical Characteristics of Plantar Warts and Association With BMI: A Retrospective Case Series Study
Plantar warts are usually rough-surfaced and slightly raised or flat, with a hard rim of thickened skin around them. They can be painful with direct pressure, especially if they sit on a weight-bearing part of the toe. If you see a small rough bump on your toe with scattered black pinpoints inside it, a wart is a strong possibility. Treatment ranges from salicylic acid preparations and cryotherapy to minor procedures for stubborn cases.
Normal Pigmentation and Ethnic Melanonychia
Not every dark line or spot on a toenail is a problem. In people with darker skin tones, longitudinal pigmented bands running along the toenail are a normal, benign finding often referred to as ethnic or racial melanonychia. These bands are caused by the routine activity of melanocytes in the nail matrix and are common in people with Fitzpatrick skin types IV and V.10PubMed Central. When all you have is a dermatoscope— start looking at the nails Multiple nails are frequently involved, and the color tends to be a homogeneous gray-brown rather than irregular or splotchy.
Beyond ethnic melanonychia, nail matrix nevi are another benign cause of pigmented bands. These are small clusters of pigment-producing cells in the nail root that produce a single brown or dark streak that stays consistent over time. Both conditions are far more common than melanoma, and neither requires treatment. The bands may widen slightly with age.11PubMed Central. Melanonychia: Etiology, Diagnosis, and Treatment
Chronic friction from tight, narrow, or pointed shoes can also trigger brown pigmentation on the big toe, fourth, or fifth toenails without any underlying disease. The pressure stimulates melanocyte activity in the nail bed, creating a discolored patch that looks worrisome but is mechanically induced and harmless.11PubMed Central. Melanonychia: Etiology, Diagnosis, and Treatment
Drug-Induced Nail Darkening
Certain medications can activate the melanocytes in the nail matrix, causing them to produce melanin that shows up as one or more longitudinal dark bands or as diffuse darkening of the entire nail plate. The color can range from brown to black depending on how many melanocytes are activated and how much pigment they produce.12Elsevier. Drug-related nail disease
Chemotherapy agents are among the most commonly reported culprits, but antimalarials, certain antibiotics, antiretroviral drugs, and some antifungals have also been linked to nail pigmentation changes. If a medication activated a limited group of melanocytes, a single pigmented stripe appears; if the activation is diffuse, the entire nail darkens. The pigmentation is usually reversible once the drug is discontinued, though it may take several months for the affected nail to grow out completely. If you notice new dark streaks on your toenails shortly after starting a medication, mention it to your prescribing doctor rather than assuming it is something sinister.
Splinter Hemorrhages
Splinter hemorrhages are thin, dark red to black lines that run vertically under the toenail. They look like tiny splinters embedded in the nail and are caused by bleeding from the small blood vessels in the nail bed. By far the most common cause is simple trauma or idiopathic occurrence, meaning they just happen sometimes without a clear trigger.13PubMed Central. Nitrofurantoin-induced splinter hemorrhages: A forgotten culprit
However, splinter hemorrhages can occasionally signal something more significant. Bacterial endocarditis, an infection of the heart valves, is the classic systemic association. Certain medications have also been linked to splinter hemorrhages.13PubMed Central. Nitrofurantoin-induced splinter hemorrhages: A forgotten culprit A single splinter hemorrhage on one toenail after bumping your foot is nothing to worry about. Multiple splinter hemorrhages appearing on several nails at once without clear trauma, especially if accompanied by fever or other symptoms, deserve a prompt medical evaluation.
When a Black Spot Could Be Melanoma
Subungual melanoma is rare, but it is the possibility that should be on your radar. It typically presents as a pigmented band or dark spot under the toenail that gradually widens, develops irregular borders, or shows uneven coloring. The big toe is one of the more common locations for this type of melanoma.
Dermatologists look for specific warning signs. In a study of pigmented nail bands, melanoma was associated with bands covering more than two-thirds of the nail width, the presence of gray and black colors together, irregularly spaced pigmented lines, and nail plate damage. A finding called Hutchinson’s sign, where the dark pigment extends from under the nail onto the surrounding skin of the cuticle or nail fold, was strongly linked to malignancy.14PubMed. Clinical and dermoscopic clues to differentiate pigmented nail bands: an International Dermoscopy Society study Another study found that irregular lines varying in color, spacing, thickness, and parallelism were significantly more common in melanoma than in any benign diagnosis.15Archives of Dermatology. Dermoscopic Examination of Nail Pigmentation
The tricky part is that early melanoma can look almost identical to a benign pigmented band or a hematoma that has not grown out. A few practical rules of thumb can help you decide when to seek evaluation:
- Change over time: A hematoma grows out with the nail. A melanoma stays in place or expands, because the pigment is being produced by abnormal cells in the nail matrix, not by trapped blood.
- No clear cause: If you cannot recall any injury and the dark spot appeared gradually, that is worth investigating.
- Pigment on skin: Dark coloring that bleeds onto the cuticle, nail fold, or fingertip skin is a red flag and should be evaluated promptly.16PubMed Central. Subungual Melanoma is Not so Rare: Report of Four Cases from India
- Single nail, new onset: A new dark band on a single nail in an adult, especially someone over 50, warrants a dermatology visit.
Subungual melanoma has a worse prognosis than melanoma on other body sites, partly because it tends to be diagnosed later. People assume it is a bruise or a fungal infection and wait months before seeking care. If in doubt, ask a dermatologist. A dermoscopic examination can usually distinguish benign from suspicious patterns without a biopsy, though a biopsy remains the definitive step when melanoma is suspected.
Diabetic Foot and Circulation Concerns
For people with diabetes, a black spot on a toe carries additional urgency. Reduced blood flow and diminished nerve sensation in the feet mean that minor wounds, blisters, and infections can go unnoticed and deteriorate quickly. In the diabetic foot, the appearance of a dark spot on the skin can indicate that a small break in the skin has already progressed to a deep infection, and that is a serious situation requiring immediate medical attention.17PubMed Central. Infections in the Diabetic Foot
Black or darkened skin on the toes in someone with diabetes or peripheral vascular disease can also indicate tissue death from inadequate blood supply. This is a different process entirely from the benign causes discussed earlier and is typically accompanied by pain (or paradoxically, no sensation at all due to neuropathy), swelling, warmth, or foul odor. If you have diabetes and notice any new dark area on your toes, do not wait to see if it grows out. Have it evaluated the same day if possible.
Corns, Calluses, and Footwear Effects
Sometimes the “spot” on a toe is not pigmented at all but is a thickened, hardened area of skin caused by chronic friction or pressure. Corns and calluses develop as a normal response to repeated mechanical stress, and they are especially common on the tops and sides of toes or between them, where tight shoes create contact pressure.18PubMed. Fortnightly Review: Callosities, corns, and calluses A corn with trapped blood from friction can look dark or black, especially in someone with a foot deformity like a hammertoe that creates a constant pressure point.
Poorly fitting footwear contributes to several of the conditions on this list. Shoes that are too tight can cause subungual hematomas. Shoes that are too loose allow the foot to slide and generate shearing forces, raising the risk of talon noir. Narrow toe boxes press on the outer toes and stimulate the melanocytes described in the friction-related melanonychia section. If you keep getting unexplained dark spots on your toes, a shoe fitting is one of the cheapest and most overlooked interventions. Athletic shoes in particular should leave about a thumb’s width of space between your longest toe and the end of the shoe, and should not compress the sides of your foot.
External Staining
Before worrying about infections or melanoma, consider whether the dark spot could simply be a stain. Dyes from new shoes, particularly dark leather shoes or those with interior linings that bleed color, can transfer pigment directly onto the skin and nails. Older literature documented cases of skin reactions and pigment transfer from shoe dyes containing certain chemical solvents.19JAMA. SHOE DYE POISONING While modern shoe dyes are much safer, color transfer to damp, sweaty feet remains common. Nail polish that has seeped through to the nail plate, garden soil, certain topical medications, and even betadine from a recent medical procedure can leave behind discoloration that looks more ominous than it is.
A stain will generally affect the surface of the nail or skin uniformly, won’t change shape over weeks, and can often be partially removed with alcohol or acetone. If you can wipe or scrub away some of the dark pigment, you almost certainly have a stain rather than a medical condition. That said, do not use this as a definitive test to rule out melanoma; if the area is truly in the skin or under the nail and you cannot remove it, proceed with a medical evaluation.