Why Is My Cut Black? When to Worry and What to Do

A cut that turns dark or black is usually just a normal scab forming as dried blood and clotting proteins harden over the wound surface. That said, genuinely black tissue in or around a wound can sometimes signal that the skin has lost its blood supply and is dying, a process called necrosis. Telling the difference between an ordinary healing scab and something more serious involves paying attention to a few straightforward clues, and understanding those clues can save you from both unnecessary panic and dangerous delay.

The Normal Reason a Cut Looks Black

When you cut yourself, blood rushes to the surface, clots, and dries. Fresh blood is bright red, but once it’s exposed to air and loses its oxygen, the hemoglobin in it darkens through shades of maroon, brown, and eventually near-black. That hardened cap of dried blood, dead cells, and fibrin is a scab, and it’s supposed to look dark. A healthy scab sits flat or slightly raised on the wound, doesn’t smell bad, and doesn’t keep getting bigger. The skin around it might be a little pink or red from normal inflammation, but that redness fades over a few days rather than spreading.

Most people who search “why is my cut black” are seeing a perfectly normal scab. The darkness is simply old blood. If the wound is small, was cleaned when it happened, and the surrounding skin looks and feels normal, you’re likely watching routine healing. But not every dark wound falls into this reassuring category.

What Black Tissue Actually Means When It’s Not a Scab

True black tissue, as opposed to a dark scab, is called eschar. It’s leathery, dry, often firmly stuck to the wound bed, and represents dead skin and sometimes deeper structures. Eschar forms when blood can no longer reach the tissue. Without blood flow, cells die, proteins break down, and the tissue dries out into a tough, dark crust. The underlying process is called coagulative necrosis, and it can happen for many different reasons, from severe infections to blocked arteries to deep pressure damage.

Distinguishing eschar from a normal scab isn’t always intuitive. A scab is typically thin, forms a shallow cap over a superficial cut, and eventually lifts at the edges as new skin grows beneath it. Eschar tends to be thicker, harder, and more tightly adherent. It may cover a wound that seems disproportionately deep for the injury you remember. And the tissue underneath eschar, once removed, often looks pale, grey, or yellowish rather than the healthy pink you’d see under a healing scab.

Infections That Turn Wounds Black

Several types of infection can cause the skin in and around a wound to die and darken. The speed and severity vary enormously depending on the organism involved.

Necrotizing fasciitis is the most feared. It’s a surgical emergency where bacteria spread rapidly along the tissue layers beneath the skin. As the infection destroys blood vessels that supply the overlying skin, the skin loses its blood supply and dies, producing dark or black patches and sometimes fluid-filled blisters with a reddish or purplish tinge.¹ The hallmark of necrotizing fasciitis is pain that seems wildly out of proportion to how the wound looks, along with fever, swelling that spreads by the hour, and a general feeling of being severely unwell. If a wound is darkening and you feel sicker than the wound seems to justify, get to an emergency room.

Certain bacteria produce black skin lesions through a different mechanism. Pseudomonas aeruginosa, for instance, can cause a condition called ecthyma gangrenosum in people with weakened immune systems. The bacteria invade and damage blood vessel walls, cutting off local circulation and producing dark, crater-like ulcers.² This is rare but happens more often in people undergoing chemotherapy, taking immunosuppressive drugs, or managing conditions like uncontrolled diabetes.

Fungal infections can also cause rapid blackening. Mucormycosis, caused by molds in the order Mucorales, invades tissue aggressively and causes fast-progressing tissue death. It’s rare in healthy people but a serious risk for those with poorly controlled diabetes or suppressed immune systems, and it can follow traumatic wounds contaminated with soil or organic debris.³

When Circulation Is the Problem

Blood flow is what keeps tissue alive. Anything that chokes off the supply to a wound can cause the tissue to turn black, even if there’s no infection involved.

Peripheral arterial disease, where cholesterol plaques narrow the arteries in the legs, is one of the most common reasons wounds on the feet and lower legs turn dark and fail to heal. When arterial narrowing becomes severe enough that resting tissue can’t get the oxygen it needs, ulcers form and necrosis follows.⁴ People with this degree of arterial disease typically have cold feet, weak or absent pulses in the foot, and pain that worsens when the leg is elevated. A minor cut in someone with advanced arterial disease can quickly become a black, non-healing wound that looks far worse than the original injury.

Diabetic foot ulcers are closely related. Diabetes damages both nerves and blood vessels, which creates a double problem: you may not feel the wound because of nerve damage, and the wound can’t heal properly because blood flow is compromised. Diabetic foot ulcers can be broadly grouped into those caused mainly by nerve damage and those involving significant artery disease, often with both contributing at once.⁵ A study comparing the two main types of diabetic foot gangrene found distinct clinical profiles: dry gangrene, where tissue slowly mummifies and blackens, tended to occur in patients with poorer circulation and higher body mass, while wet gangrene, involving more active infection, showed higher inflammatory markers and faster progression.⁶ Either type warrants urgent medical care.

Venous problems can also darken the skin around wounds on the lower legs, though the mechanism is different. In chronic venous insufficiency, blood pools in the leg veins and red blood cells leak into surrounding tissue. As those cells break down, they leave behind hemosiderin, an iron-storage pigment that stains the skin brown or dark brown. This brownish-black discoloration, common around the ankles and lower calves, isn’t necrosis and isn’t immediately dangerous, but it signals ongoing venous disease that makes wounds in the area slower to heal.⁷

Pressure Injuries and Deep Tissue Damage

People who are bedridden, wheelchair-bound, or have limited mobility can develop pressure injuries where sustained force compresses the skin and underlying tissue against bone. Deep tissue injury, a type of pressure damage, can appear as a purple or maroon discoloration that quickly evolves into a black eschar over the affected area. In people with lighter skin, the classic sign is a dark purple patch with a defined border. In people with darker skin tones, the discoloration can be harder to see, and clinicians are advised to look for persistent changes in skin color and areas that don’t blanch when pressed rather than relying on the purple-maroon appearance alone.⁸

Deep tissue injuries are tricky because the damage starts in the muscle and fat beneath the skin before it becomes visible on the surface. By the time the skin looks black, significant tissue underneath may already be dead. This is why pressure injuries can seem to appear suddenly, going from slightly discolored skin to a hard black patch in a matter of days.

Medications and Chemical Exposure

Some dark wound discoloration has nothing to do with infection or poor circulation. Certain medications and chemical exposures can cause skin around a wound to turn black.

Warfarin, a commonly prescribed blood thinner, can in rare cases trigger skin necrosis, usually within the first few days of treatment. This happens most often in people who have an underlying clotting tendency or who are started on warfarin at high doses without an overlapping course of another blood thinner. The skin darkens, forms eschar, and the damage can be extensive if the medication isn’t stopped promptly.⁹

Silver nitrate, used in some wound-care products and cautery sticks, can stain the skin a deep brown or black. The discoloration is caused by the silver compound reacting with light and tissue, not by tissue death. It can look alarming, mimicking the appearance of something as serious as melanoma, but the staining is reversible and the skin underneath is healthy.¹⁰ If you’ve recently had silver nitrate applied to a wound and the area looks dark, that’s almost certainly the explanation.

Traumatic Tattoos and Embedded Debris

A wound that heals with a persistent dark or bluish-black patch might not involve dead tissue at all. In injuries like road rash, explosions, or burns, foreign particles such as asphalt, dirt, metal fragments, or fuel residue can get driven into the deeper layers of skin. When the wound heals over those embedded particles, the result is what’s called a traumatic tattoo, a permanent dark mark that looks a lot like an ink tattoo.¹¹

Traumatic tattoos are cosmetically bothersome but medically benign. The foreign material is inert and trapped in the dermis, so it doesn’t usually cause ongoing infection or tissue damage. Treatment is elective and typically involves laser therapy or dermabrasion to remove the pigment.¹² If a wound from a road accident or similar event heals with a flat dark stain that doesn’t change, get it checked to confirm it’s just embedded debris, but don’t assume it means the tissue is dying.

Frostbite

Cold exposure severe enough to freeze tissue can produce dramatic blackening. In deep frostbite, ice crystals form inside cells, blood vessels clamp shut, and the affected tissue dies from a combination of freezing damage and loss of blood flow. After rewarming, large blisters may form within a day or two, and the dead tissue gradually turns black and hard as it dries out.¹³ The blackened tissue from frostbite often looks like a thick, rigid shell over the affected fingers, toes, or ears. The extent of the damage isn’t always obvious immediately, and surgeons often wait weeks before deciding how much tissue needs to be removed, because some areas that initially look dead can recover partial blood flow.

Rare but Worth Knowing

A few less common conditions also cause black wound-like lesions. Cutaneous anthrax, caused by the bacterium Bacillus anthracis, classically produces a painless black eschar on the skin after exposure to infected animals or animal products. The lesion starts as a small bump, develops blisters, and then forms a characteristic dark, depressed scab surrounded by swelling.¹⁴ The word “anthrax” itself comes from the Greek word for coal, a reference to this distinctive black eschar.¹⁵ This is extremely rare in most developed countries but still occurs in agricultural regions worldwide.

Tick-borne diseases like Rocky Mountain spotted fever can also produce dark necrotic skin lesions. The bacteria infect blood vessel walls, triggering clots that block local circulation and cause patches of skin to die. Studies of these lesions have confirmed that the darkened areas correspond to sites of extensive bacterial infection with damage to numerous local blood vessels, forming necrotic eschars.¹⁶

Finally, melanoma occasionally mimics a non-healing wound or develops within what appears to be a chronic ulcer. A dark, irregularly pigmented wound that doesn’t respond to normal wound care, especially on the lower leg, deserves a biopsy. One case report described a leg ulcer initially treated as a vascular wound that turned out to be advanced melanoma with satellite nodules and signs of local spread.¹⁷ This is uncommon, but it’s a good reason not to ignore a wound that looks unusual and refuses to heal.

Red Flags That Mean You Should See a Doctor

Not every dark wound is an emergency, but certain signs should prompt you to seek medical attention sooner rather than later:

• Spreading redness: Red streaks radiating away from the wound, or a border of redness that’s visibly expanding over hours, suggests the infection is moving into surrounding tissue.
• Severe or worsening pain: A wound that hurts more than you’d expect, or pain that’s getting worse rather than better over days, can indicate a deeper infection like necrotizing fasciitis.
• Fever or chills: Systemic symptoms suggest the infection has moved beyond the wound itself.
• Foul smell: A strong, unpleasant odor from the wound indicates tissue breakdown, often from bacterial overgrowth in dead tissue.
• Numbness: Loss of feeling around the wound, particularly in the feet or hands, may signal nerve damage or deep tissue death.
• No improvement after two weeks: A minor cut should show clear progress toward healing within a week or two. A wound that stalls or worsens needs professional evaluation.

People with diabetes, peripheral artery disease, or weakened immune systems should have a lower threshold for seeking care. A cut that would be trivial on a healthy 25-year-old’s forearm can become a serious problem on the foot of someone with diabetes and poor circulation.

What Treatment Looks Like

When black tissue in a wound does represent necrosis, the standard medical approach is debridement, which means removing the dead material so the wound can heal. Debridement clears away the necrotic tissue, reduces bacterial load, improves local blood flow to the wound bed, and lowers inflammation, all of which help the remaining healthy tissue recover.¹⁸ There are several methods, from sharp surgical removal to enzyme-based ointments that gradually dissolve dead tissue, and the choice depends on factors like wound location, depth, the underlying cause, and what the patient can tolerate.

For wounds caused by blocked arteries, debridement alone isn’t enough. If blood flow isn’t restored through procedures like angioplasty or bypass surgery, the new tissue will die for the same reason the old tissue did. Treating the underlying circulation problem is just as important as cleaning the wound. The same principle applies to infected wounds: antibiotics or antifungals address the organism driving the necrosis, and debridement clears the dead tissue left behind.

At home, before you reach a doctor, keep the wound clean, avoid applying random topical remedies (hydrogen peroxide and rubbing alcohol can damage healthy tissue), and cover it with a clean bandage. Don’t attempt to pull off firmly attached black tissue yourself. What looks like a removable scab might be eschar sitting over fragile tissue, and removing it improperly can cause bleeding, introduce bacteria, or damage tissue that was beginning to recover underneath.

Why Dark Skin Tones Make Assessment Harder

Much of wound assessment relies on color changes in the skin, redness for inflammation, purple or maroon for deep injury, pale or white for poor blood flow. These visual cues were largely described using lighter skin tones as the reference, which creates real diagnostic challenges for people with darker skin. The early purple discoloration of a deep tissue injury, for example, can be invisible on dark brown or black skin. Clinicians working with darker-skinned patients are encouraged to rely more on whether skin blanches under pressure, changes in skin texture or temperature, and the patient’s reported symptoms rather than color alone.⁸

If you have darker skin and notice a wound that feels harder, warmer, or more painful than you’d expect, or if the surrounding skin feels different in texture compared to the other side of your body, mention these changes to your doctor even if the color difference doesn’t look dramatic. These tactile and sensory cues can be just as informative as visual ones and may catch problems earlier than waiting for obvious color changes.