What Do Skin Ulcers Look Like? Types & Pictures

Skin ulcers are open sores where the top layers of skin have broken down, exposing deeper tissue underneath. They range from shallow, weeping patches the size of a coin to deep craters that reach muscle or bone, and their shape, color, and location vary dramatically depending on what caused them. A venous ulcer on the lower leg looks nothing like a diabetic ulcer on the sole of the foot or a pressure sore on the tailbone, and recognizing those differences is often the first step toward getting the right treatment.

What All Skin Ulcers Have in Common

Despite the variety, most skin ulcers share a basic anatomy. There is an open wound bed, which can be red, yellow, grey, or black depending on the tissue health. Surrounding the wound bed is a border or edge, which might slope gently, roll inward, or look sharply “punched out.” Beyond that border sits the periwound skin, the area immediately around the ulcer that often shows color changes, swelling, or texture differences that hint at the underlying cause. A proper wound assessment records the size, depth, edge characteristics, and the type of tissue in the wound bed, along with any discharge or odor.¹

A wound bed filled with bright red, bumpy tissue (granulation tissue) is generally a sign of active healing. Yellow or grey material covering the base is slough, a mix of dead cells and protein. Black, leathery tissue is necrotic, meaning it has died and dried out. Many ulcers contain a patchwork of all three, and tracking how those proportions shift over time tells clinicians whether the wound is improving or stalling.¹

Venous Leg Ulcers

Venous ulcers are the most common type of chronic leg ulcer, and they have a fairly recognizable look. They tend to sit in the “gaiter area” of the lower leg, roughly between the ankle and mid-calf, where blood pools due to faulty vein valves. The ulcer itself is usually shallow with gently sloping edges and a wound bed that is red or covered in yellowish slough. What really sets venous ulcers apart is the skin around them. You’ll often see brown or rust-colored staining from hemosiderin, a pigment left behind when red blood cells leak out of swollen veins and break down. The surrounding skin may also feel hard and woody, a condition called lipodermatosclerosis, and it can look eczema-like with flaking and redness.²

Swelling in the leg, especially by the end of the day, is another hallmark. The ulcers themselves are not usually as painful as arterial ulcers, though they can ache when you’re standing for long periods. They tend to be irregularly shaped and can grow quite large if left untreated, sometimes wrapping partway around the ankle.

Arterial Ulcers

Arterial ulcers look strikingly different from venous ones and appear in different places. Because they’re caused by poor blood supply rather than blood pooling, they favor the toes, tops of feet, heels, and bony pressure points on the lower leg. The classic description is a “punched out” appearance: the edges are sharp and well defined, as if someone used a hole punch on the skin, and the wound bed is pale, grey, or yellowish because so little blood is reaching the area.²

The skin around an arterial ulcer often tells its own story. It tends to be cool to the touch, shiny, and hairless, with thin, fragile-looking tissue. If you press the skin and release, color returns slowly because blood flow is compromised. Pulses at the ankle or top of the foot may be weak or absent. Pain is a major feature, particularly at night or when the legs are elevated, because gravity is no longer helping push blood downward.

Diabetic Foot Ulcers

Diabetic ulcers most commonly form on the sole of the foot, particularly under the ball of the foot and on the heel. Nerve damage (neuropathy) means people often don’t feel the ulcer forming, so it can go unnoticed until it’s well established. Plantar and heel ulcers typically have a central depression surrounded by a thickened, callus-like border with a ring of hard, built-up skin around the outside.³

The wound bed can range from pink granulation tissue to grey slough, and because sensation is dulled, these ulcers can deepen rapidly without the person realizing it. It’s worth knowing that diabetic ulcers don’t all look the same: a purely neuropathic ulcer on a warm, well-perfused foot looks quite different from a neuro-ischemic ulcer where blood flow is also compromised. In a large study comparing these two subtypes, ischemic diabetic ulcers were more likely to be large (over 5 cm²), deep enough to probe to bone, and infected, and they carried far worse outcomes including higher rates of amputation and death.⁴

A neuropathic ulcer on a warm foot with good pulses is concerning but treatable. An ischemic ulcer on a cold, pale foot with absent pulses is a different situation entirely and generally needs vascular evaluation urgently.

Pressure Ulcers

Pressure ulcers, commonly called bedsores, develop where bone presses against skin for prolonged periods. The sacrum (lower back), heels, hips, and shoulder blades are the most common sites. Early-stage pressure injuries may not look like an open wound at all. In people with lighter skin, the first sign is a patch of redness that doesn’t blanch when you press on it. In later stages, the skin breaks open, and the ulcer can deepen through fat, muscle, and all the way to bone.

What makes pressure ulcers tricky to evaluate is that even trained wound specialists don’t always agree on what they’re seeing. A study of nurses using both bedside and photographic assessment found only fair to moderate agreement on staging pressure ulcers, and slight agreement on surrounding skin color.⁵ That inconsistency underscores how difficult visual assessment alone can be, particularly through photographs.

How Skin Tone Changes What You See

Most wound-care training materials were developed using images of lighter skin, and this creates a real clinical blind spot. The redness that signals early pressure damage in pale skin may appear as a darkening, purplish hue, or subtle color shift in darker skin tones. In qualitative research with patients and carers, the most commonly recognized early sign of pressure damage in people with dark skin was a patch that looked darker than the surrounding area, rather than red.⁶

The challenge extends beyond early detection. The hemosiderin staining around venous ulcers, the pale base of arterial ulcers, and the erythema that signals infection all present differently across the spectrum of skin tones. Wound-care experts have called for better assessment techniques and more diverse representation in educational materials, because relying on descriptions calibrated to lighter skin misses early damage in a substantial portion of patients.⁷ If you’re checking your own skin or a family member’s, pay attention to temperature changes (warmth or coolness compared to surrounding areas), firmness, and pain or tenderness, not just color.

Mixed Arterial-Venous Ulcers

Not every leg ulcer fits neatly into the “venous” or “arterial” box. A significant number involve both poor vein function and reduced arterial supply, and these mixed ulcers tend to be harder to treat because the standard compression therapy for venous disease can be dangerous when arteries are also compromised. Visually, mixed ulcers borrow features from both types: the leg may show the hyperpigmentation and skin changes of venous disease, but the limb is cool, hairless, and shiny with weak pulses, suggesting arterial problems too. These ulcers are often deeper and more likely to be covered with black, leathery eschar than purely venous ulcers.⁸

Clinical examination of mixed ulcers often reveals cool extremities, cracked and inelastic skin, slow capillary refill, and weak foot pulses.⁹ These overlapping features mean that looking at the ulcer alone won’t tell you the full story. You need the whole picture, including the surrounding skin, the temperature of the limb, and pulse checks, to figure out what’s going on.

Pyoderma Gangrenosum

Pyoderma gangrenosum is an inflammatory condition that produces ulcers with an unmistakable and alarming appearance. It typically starts as a small, painful pustule or blister that rapidly breaks down into a deep ulcer. The hallmark is a dusky purple or violaceous border with undermined edges, meaning the edges overhang a cavity underneath. A case report in the BMJ described a lesion that began as a 2×2 cm purulent ulcer with purple borders and surrounding redness, then expanded to 9×7 cm with undermined edges.¹⁰

What makes pyoderma gangrenosum especially important to recognize is that it exhibits pathergy: trauma to the skin, including surgical debridement, can make it worse. The ulcers look so much like infected wounds that they’re sometimes mistakenly treated with aggressive surgical cleaning, which only accelerates the destruction. The wound bed is often boggy with a purulent or necrotic base, and the surrounding skin can be inflamed and tender. If you see a rapidly expanding ulcer with those distinctive purple, undermined borders, pyoderma gangrenosum should be on the radar.

Calciphylaxis Ulcers

Calciphylaxis is a rare and serious condition most often seen in people with advanced kidney disease. Calcium deposits block small blood vessels in the skin, leading to tissue death. The early visual signs are subtle and easy to miss: patches of redness or purplish discoloration and intense pain, sometimes in a net-like pattern called livedo reticularis. As the condition progresses, the skin develops dark, irregular purpura that evolve into black necrotic ulcers.¹¹

These ulcers can appear on the thighs, abdomen, and buttocks as well as the lower legs. The pain is often described as excruciating, out of proportion to what you’d expect from the size of the wound. Calciphylaxis carries high mortality, so early recognition of those initial purplish patches, especially in someone on dialysis, is genuinely life-saving.

Malignant Ulcers

A Marjolin ulcer is a type of cancer that develops in an area of chronic scarring, such as an old burn wound or a long-standing non-healing ulcer. These are typically flat and hardened with raised, rolled margins. A less common variant grows outward with finger-like projections, giving it a bumpy, papillary appearance.¹²

The key warning sign is change. Any chronic wound or old scar that suddenly starts growing, bleeds easily, develops raised or irregular edges, or produces a foul-smelling discharge should be biopsied. Marjolin ulcers can develop decades after the original injury, so the history of trauma may feel ancient and irrelevant. They’re not the only malignant ulcer: basal cell carcinoma and squamous cell carcinoma can also present as non-healing ulcers with pearly or rolled borders, and melanoma occasionally ulcerates. The general rule is that any wound that looks like it should be healing but isn’t, especially with an irregular or hardened edge, deserves a closer look.

Infectious Ulcers

Some skin ulcers are caused directly by infection rather than by circulation problems or pressure. Buruli ulcer, caused by Mycobacterium ulcerans, starts as a painless skin nodule that progressively ulcerates as the tissue underneath dies.¹³ It’s primarily a tropical disease, but the characteristic painless expansion is distinctive and unlike most other ulcer types.

Leishmaniasis, another tropical infection, produces ulcers that can look alarmingly like skin cancer: round, crater-like sores with raised borders. These typically appear on exposed skin where sandflies have bitten. In temperate climates, ulcerating infections are less exotic but still occur: ecthyma, for instance, produces punched-out ulcers with thick crusts, usually on the legs, and can be caused by streptococcal or staphylococcal bacteria. The shared thread among infectious ulcers is that treating the wound without treating the infection won’t work.

Drug-Induced Ulcers

Certain medications can cause skin ulcers that look confusingly similar to venous or arterial disease. Hydroxyurea, used to treat blood disorders, can produce ulcers that are usually small, shallow, and well defined, with a yellow, fibrinous base. They tend to appear around the ankles and are often bilateral, showing up on both legs.¹⁴ These ulcers are notoriously stubborn and resist healing as long as the drug is continued.

Nicorandil, a medication used for angina, is another culprit. It tends to cause ulcers on mucosal surfaces like the mouth and anus, though skin ulcers can also occur. A French pharmacovigilance study found that nicorandil-induced ulcers were mainly mucosal, with a history of prior trauma at the site in roughly a quarter of cases.¹⁵ If you develop a new ulcer while taking any medication, it’s worth asking whether the drug could be responsible, because the only real treatment is stopping or switching the offending agent.

Signs That an Ulcer Is Infected

Any chronic ulcer can become infected, and recognizing infection by sight and smell is important because it changes the urgency and treatment. Clinicians use a set of signs to distinguish surface-level bacterial overgrowth from deeper infection. Superficial bacterial damage is suggested when three or more of these are present: a wound that has stopped progressing, increased discharge, red and fragile granulation tissue, dead debris on the wound surface, and smell. For deeper infection, the signs include an ulcer that’s growing rather than shrinking, increased warmth, exposed bone on probing, new areas of skin breakdown around the edges, redness and swelling in the surrounding skin, increased discharge, and smell.¹⁶

In venous ulcers specifically, certain visual indicators stand out. Discoloration of a dark, opaque, or brick-red quality and increased amounts of discharge were the two most common infection indicators found in one study, appearing in more than 70% of infected cases.¹⁷ Interestingly, the visual signs didn’t predict whether the infecting bacteria were resistant to antibiotics or not, so the appearance tells you an infection is present but doesn’t tell you which bug is responsible.

Self-Inflicted Ulcers

Factitial ulcers, sometimes called dermatitis artefacta, are wounds that a person creates or maintains on their own body, often in the context of psychological distress. These can be among the hardest ulcers to identify because they don’t follow the rules of any recognized disease pattern. Clues include unusual shapes (geometric, linear, or bizarrely irregular), locations limited to areas the person can easily reach, a clear boundary between damaged and normal skin, and a history of wounds that don’t respond to any treatment.¹⁸

These ulcers raise sensitive issues. The person may not consciously acknowledge what they’re doing, and confrontation tends to be counterproductive. If you or a healthcare provider suspects self-inflicted wounds, psychiatric and psychological support is the most helpful path forward. The wounds themselves often heal readily once the behavior stops, which also serves as a diagnostic clue: rapid improvement when the area is covered and inaccessible points toward a factitial origin.

When Location Alone Narrows It Down

If you’re trying to figure out what type of ulcer you’re looking at, the location on the body is one of the strongest initial clues. Inner ankle and lower calf ulcers with brown-stained surrounding skin point strongly toward venous disease. Toes, heels, and bony prominences on cold, pale feet suggest arterial insufficiency. The sole of the foot, particularly under a callus, is the classic site for diabetic neuropathic ulcers. Sacrum, heels, and hip areas in someone with limited mobility suggest pressure injury. Mucosal surfaces in someone taking nicorandil or hydroxyurea raise the possibility of a drug reaction. And ulcers confined to easily accessible body areas in geometric or bizarre shapes raise the question of factitial origin.

Location doesn’t replace a proper evaluation, but in a situation where you’re trying to decide how urgently to seek care, it can guide your thinking. An ulcer on the toe of someone with diabetes and cold feet, for example, needs same-day evaluation. A slowly expanding shallow ulcer around the ankle in someone with varicose veins and leg swelling still needs attention, but the timeline is less frantic.

What a Healing Ulcer Looks Like Versus a Stalled One

Understanding what healing looks like can save you from unnecessary panic or false reassurance. A wound that’s actively improving shows bright red, healthy-looking granulation tissue filling the base, and the edges gradually migrate inward. The wound gets smaller in measurable ways over weeks. Discharge decreases and becomes clear or slightly yellow rather than thick or foul-smelling.

A wound that has stalled often has a pale, dusky wound bed rather than a vivid red one. It may be covered in persistent slough that resists removal, or it shows no measurable size reduction over several weeks.¹ Black necrotic tissue covering the base is an obvious sign that something is wrong, though small amounts of dry eschar on a heel wound are sometimes left in place intentionally as a natural biological dressing. The edges of a stalled wound may become rolled or thickened rather than actively migrating, a sign that the normal healing process has broken down and the wound needs reassessment.