A dark spot on your toe is most often a subungual hematoma, which is blood trapped under the toenail after an injury. Stubbing your toe, dropping something on it, or wearing tight shoes during exercise can rupture tiny blood vessels beneath the nail plate, leaving a red-to-black mark that may take weeks or months to grow out. But trauma is only one possibility on a surprisingly long list, and some causes need medical attention while others are purely cosmetic. Understanding the differences matters because certain marks that look harmless can signal something serious, and certain alarming-looking spots turn out to be completely benign.
Trauma and Subungual Hematoma
The single most common reason for a dark spot on a toe is bleeding beneath the nail. A subungual hematoma forms when blood pools between the nail plate and the nail bed after a blow or repeated pressure.1PubMed Central. Subungual Hematoma: Insights From a Clinical Case Study The discoloration typically starts out reddish and darkens to a deep purple or black over a few days. Under a dermatoscope, these spots show up as well-defined dots or blotches with red-to-black pigmentation, distinct from the irregular patterns seen in melanoma.2British Journal of Dermatology. Dermoscopy of subungual haemorrhage: its usefulness in differential diagnosis from nail‐unit melanoma
You may not even remember the injury that caused it. Runners and hikers frequently develop hematomas from repetitive impact against the front of the shoe, especially on the big toe or second toe. As the nail grows, the dark spot migrates outward and eventually disappears, though that process can take six to nine months on a toenail because toenails grow slowly. If the spot does not move with the nail, that’s a reason to see a dermatologist.
Talon Noir and Skin-Level Bruising
Not every dark spot sits under the nail. Talon noir (French for “black heel,” though it occurs on toes and the forefoot too) is caused by shearing forces that damage tiny blood vessels in the upper layer of skin, letting blood leak into the surrounding tissue.3PubMed Central. Talon Noir: A Case Report and Literature Review It is classically associated with sports, but ill-fitting shoes, walking long distances, and conditions like diabetes that impair healing can also produce these pigmented patches.3PubMed Central. Talon Noir: A Case Report and Literature Review Talon noir tends to look like a cluster of dark specks rather than a single solid spot. It is harmless and usually fades on its own once the repetitive pressure stops.
Longitudinal Melanonychia
If the dark mark on your toe looks like a stripe running the length of the nail, you may be looking at longitudinal melanonychia. This is a brown-to-black band on the nail plate caused by melanin deposited as the nail grows from its root (the matrix). The possible triggers range from completely benign to potentially dangerous.4PubMed Central. Melanonychia: Etiology, Diagnosis, and Treatment
On the benign end, melanonychia can come from a small mole (nail matrix nevus) or a lentigo in the nail matrix, from certain medications, from normal ethnic variation, or from friction and trauma activating melanocytes to produce extra pigment.5PubMed. Evaluation and diagnosis of longitudinal melanonychia: A clinical review by a nail expert group On the dangerous end, a band of melanonychia can be the earliest visible sign of nail-unit melanoma. Because the causes look similar on the surface, a single pigmented band on one nail in an adult warrants closer examination, and biopsy remains the gold standard for a definitive diagnosis.6PubMed Central. Use of Nail Dermoscopy in the Management of Melanonychia: Review
Melanonychia that appears on multiple nails simultaneously is generally less worrisome than a band on a single nail, because multi-nail pigmentation more commonly reflects systemic causes such as medications, hormonal changes, or normal variation in people with darker skin tones.
Infections That Darken the Toe
Fungal and bacterial infections can both deposit pigment in or around the nail. Certain fungi, including Candida and Aspergillus species, produce dark pigment that can mimic melanonychia. In documented cases, the nail discoloration improved after antifungal treatment, though recurrence on another nail was possible.7Pigment International. Pigmentary changes associated with endocrine and metabolic disorders Fungal melanonychia is worth keeping in mind because it is treatable and does not require biopsy once a culture confirms the organism.
Pseudomonas aeruginosa, a common environmental bacterium, produces a blue-green pigment that gives infected nails a distinctive greenish-black appearance known as chloronychia or “green nail syndrome.”8PubMed. Retrospective Case Series on Risk Factors, Diagnosis and Treatment of Pseudomonas aeruginosa Nail Infections It tends to develop in people whose hands or feet spend a lot of time in damp environments, or in elderly individuals with chronic nail separation (onycholysis).9PubMed Central. Chloronychia: green nail syndrome caused by Pseudomonas aeruginosa in elderly persons The color is more green than black, which helps distinguish it from melanin-based discoloration, but in dim light or when mixed with old blood, the distinction is not always obvious.
Medications and Systemic Conditions
Several classes of drugs can cause darkening of the nails and surrounding skin. Chemotherapy agents, antimalarials, tetracycline antibiotics, retinoids, and zidovudine (an antiretroviral) are well-documented offenders.10PubMed. Drug-induced nail disorders: incidence, management and prognosis The pigment change may show up as a dark band on one or more nails or as diffuse darkening of the nail plate. Antimalarials bind to melanin in the skin, while the mechanism behind chemotherapy-related pigmentation is less well understood but likely involves the outer layers of the skin.11PubMed. Drug- and heavy metal–induced hyperpigmentation If you started a new medication shortly before noticing a dark spot on your toe, mention the timeline to your doctor.
Endocrine disorders can also leave their mark. Addison’s disease, in which the adrenal glands produce insufficient cortisol, triggers widespread darkening of the skin that is especially noticeable on sun-exposed areas, scars, knuckles, palmar creases, and nails.12PubMed Central. Addisonian Pigmentation – The Great Mimicker – A Review People with Addison’s disease may develop longitudinal bands on multiple nails along with general skin darkening and darkening of existing moles.7Pigment International. Pigmentary changes associated with endocrine and metabolic disorders These changes develop gradually and affect many areas of the body, so an isolated dark spot on one toe is unlikely to be Addison’s disease. But if you have darkening across several nails along with fatigue, low blood pressure, and salt cravings, the combination warrants bloodwork.
When to Worry About Melanoma
Acral lentiginous melanoma (ALM) is a form of skin cancer that arises on the palms, soles, and beneath the nails. It is relatively rare overall, but it is the most common type of melanoma on the feet, and it tends to be diagnosed at a more advanced stage because people and even clinicians sometimes mistake it for a bruise or a benign mole. In one study of 126 patients with ALM, the average thickness at diagnosis was about two and a half millimeters, which is considered thick and correlates with a worse prognosis.13British Journal of Dermatology. Acral lentiginous melanoma: a clinicoprognostic study of 126 cases About a third of the lesions were on or under the nail, with the rest on soles, palms, and nearby skin.
ALM does not follow the usual melanoma risk profile. There was no evidence of overexposure to UV radiation in those 126 patients, and no predisposing genetic trait was identified.13British Journal of Dermatology. Acral lentiginous melanoma: a clinicoprognostic study of 126 cases Sun protection, while important for other parts of the body, does not explain or prevent this type of melanoma. Roughly a third of ALM cases are amelanotic, meaning they lack visible pigment, which makes them even easier to miss.14British Journal of Dermatology. Dermoscopic features of acral lentiginous melanoma in a large series of 110 cases in a white population When pigment is present, dermoscopy often reveals irregular lines that vary in color, spacing, and width, or a “parallel ridge” pattern on volar skin.
Populations of African descent have a higher incidence of foot-sole melanoma compared to other groups, which largely explains the elevated rate of ALM in that demographic.15British Journal of Cancer. Racial differences in melanoma incidence This is a critical point because darker-skinned individuals are sometimes told they don’t need to worry about melanoma. They do, especially on the feet and under the nails.
Hutchinson’s Sign and Its Limitations
One clinical clue doctors look for is Hutchinson’s sign: dark pigmentation spreading from a nail band into the surrounding skin of the cuticle and nail folds. First described in 1886, it has long been considered a strong indicator of subungual melanoma.16PubMed. Hutchinson’s sign: a reappraisal A biopsy is strongly recommended whenever this sign appears.17Actas Dermo-Sifiliográficas. Is Hutchinson’s Sign Pathognomic of Subungual Melanoma?
However, Hutchinson’s sign is not foolproof. False positives occur in a range of benign conditions, including ethnic pigmentation, trauma, radiation therapy, certain medications like minocycline, congenital moles, and even hormonal conditions like hyperthyroidism.17Actas Dermo-Sifiliográficas. Is Hutchinson’s Sign Pathognomic of Subungual Melanoma? The term “pseudo-Hutchinson’s sign” describes situations where pigment in the nail bed or matrix shows through the translucent nail fold, mimicking the spread of pigmentation without any actual invasion.16PubMed. Hutchinson’s sign: a reappraisal The mere presence of periungual pigmentation is not, on its own, proof of melanoma.18PubMed. Non-melanoma Hutchinson’s sign: a reappraisal of this important, remarkable melanoma simulant This is important to understand because it means that the sign should prompt evaluation rather than panic.
How Doctors Evaluate a Dark Spot on the Toe
The first tool a dermatologist reaches for is a dermatoscope, a handheld magnifying device with polarized light that reveals structures beneath the skin surface invisible to the naked eye. Dermoscopy has become the standard for evaluating pigmented skin lesions because it substantially improves diagnostic accuracy compared to visual inspection alone.19PubMed. Dermoscopy of melanoma according to different body sites: Head and neck, trunk, limbs, nail, mucosal and acral
For nail pigmentation specifically, dermoscopy can distinguish between the regular, parallel lines of a benign mole and the irregular, multicolored lines associated with melanoma. In one study comparing dermoscopic features across diagnoses, the combination of a brown background with lines that were irregular in color, spacing, thickness, and parallelism was strongly associated with melanoma.20Archives of Dermatology. Dermoscopic Examination of Nail Pigmentation The same study found that pigmentation visible in the cuticle only under the dermatoscope (the micro-Hutchinson sign) appeared in a small number of cases but was exclusively seen in melanoma.
Benign moles on volar skin (soles and palms) show characteristic dermoscopic patterns too. In a study of over 200 volar lesions, more than half showed a “parallel furrow” pattern, and none exhibited the parallel ridge pattern associated with melanoma.21JAMA Dermatology. Dermoscopic Patterns of Benign Volar Melanocytic Lesions in Patients With Atypical Mole Syndrome So the patterns a dermatologist sees under magnification carry real diagnostic weight.
When dermoscopy is inconclusive, a nail biopsy is the next step. This can involve removing a small piece of the nail plate, the nail bed, or the nail matrix for microscopic examination. The procedure is done under local anesthesia, and while it carries a small risk of permanent nail changes, it provides a definitive answer.22PubMed Central. Nail Biopsy: A User’s Manual Choosing the right site for biopsy matters: the pigment’s origin (nail matrix, nail bed, or surrounding skin) determines which type of biopsy is most informative.
Vascular Causes and Cholesterol Emboli
Not every dark toe spot involves pigment. Reduced blood flow to the toes can cause tissue to darken, and the causes range from benign growths to serious vascular disease. Glomus tumors, for instance, are small, painful vascular growths that can develop under the toenail and produce a dark-blue or purple spot. They are rare and typically cause intense, disproportionate pain when the toe is exposed to cold or pressure.23PubMed Central. Glomus tumour of the fourth toe: case discussion and review of literature
In older adults with atherosclerosis, cholesterol-rich debris can break off from arterial plaques and travel downstream, lodging in the tiny arteries of the toes. This produces focal areas of ischemia that appear as blue or dusky discoloration on individual toes, a condition sometimes called “blue toe syndrome” or “trash foot.”24JAMA. Lower-Extremity Arterial Emboli From Ulcerating Atherosclerotic Plaques It often happens after vascular procedures or anticoagulant therapy dislodges plaque material. If a previously normal toe turns dusky with intact pulses elsewhere, cholesterol embolization is on the differential.
Smartphone Apps and Their Limits
If you’ve been tempted to photograph your dark toe spot and run it through a skin-cancer detection app, the technology is advancing but has real limitations. In a prospective study of an artificial-intelligence-based smartphone app, image capture failed entirely in about one in six attempts even under optimal conditions. When photos were successfully analyzed, the app’s neural network detected skin cancer with a sensitivity of about 83% and specificity around 77%.25PubMed. Artificial intelligence-based smartphone application for skin cancer detection: a prospective diagnostic accuracy study Sensitivity was lower for melanocytic lesions specifically, meaning the app was more likely to miss a mole-related cancer than a non-melanocytic one. When real-time teledermatology review was added on top of the AI analysis, specificity improved but sensitivity actually dipped. And in user hands, successful image capture dropped to under 30%.
An app that misses roughly one in five skin cancers and fails to capture a usable photo most of the time in real-world conditions is a screening aid at best. It cannot replace a dermatologist and a dermatoscope, and a negative result from an app should not reassure you that a changing spot on your toe is safe.
Why People Wait Too Long
One of the most consistent findings in foot-health research is that people delay seeking care for worrying changes on their feet far longer than they would for the same changes on their face or hands. Interviews with patients who eventually required toe amputations found that delays happened for layered reasons: not recognizing that something was wrong, misinterpreting symptoms as minor, competing life priorities, and even being told by initial healthcare providers to “watch it” rather than investigate.26PLOS ONE. How patients interpret early signs of foot problems and reasons for delays in care: Findings from interviews with patients who have undergone toe amputations Transportation barriers and difficulty accessing specialists added further delay.
A dark spot on a toe sits in a perfect storm for delayed care. Feet are out of sight most of the day, the spot may not hurt, and people often assume it’s just a bruise or a fungal infection. The average thickness of ALM at diagnosis speaks to this pattern: by the time the lesion is biopsied, it has often been growing unnoticed for months or years. Checking your toes during nail trimming and noting any new marks, any band that widens over time, or any spot that does not grow out with the nail are low-effort habits that improve your odds of catching something early. If a spot lasts more than a few weeks without an obvious traumatic explanation, a visit to a dermatologist is a reasonable next step, not an overreaction.