A skin ulcer is an open sore that breaks through the outer layer of skin and fails to heal on its own within a normal timeframe. Most look like a shallow crater or a punched-out hole with distinct edges, and the tissue inside may be red, yellow, black, or a mix of colors depending on how much damage has occurred. They range from a mild irritation to a deep wound that reaches muscle or bone, and the type matters because each one has a different cause and needs a different approach.
What Do Skin Ulcers Look Like?
The appearance of a skin ulcer depends on its stage, its cause, and where it sits on the body. A typical ulcer has a visible break in the skin with a rim of tissue around it. The center may be clean and pink, or it may hold yellowish debris, dark dead tissue, or a thick discharge.
Several visual features tend to show up:
- Shape: Often round or oval, with a “punched-out” look and clear borders. Some ulcers have irregular, ragged edges.
- Color of the wound bed: Pink or red suggests healthy healing tissue. Yellow or cream-colored tissue often means slough, a mix of dead cells and fluid. Black or brown tissue is eschar, which is dead tissue that needs medical attention.
- Surrounding skin: May be red, warm, swollen, or shiny. In poor circulation, the skin around the ulcer can look pale, cool, or tight.
- Drainage: Clear or light fluid is common. Thick, foul-smelling, or pus-like drainage can point to infection.
- Depth: Some ulcers are superficial scrapes. Others form a deep cavity that extends into fat, muscle, tendon, or bone.
An ulcer is not the same as a scrape or a cut. A scrape heals as new skin grows across it. An ulcer keeps breaking down because the underlying cause — pressure, poor blood flow, nerve damage, or another condition — is still active. That is why the cause has to be treated, not just the wound.
One detail people often miss: an ulcer can look mild on the surface while being serious underneath. A small opening on a heel or the base of the spine can hide damage that extends deep into tissue. Size alone is a poor guide to how serious an ulcer is.
What Are the Main Types of Skin Ulcers?
Clinicians usually group skin ulcers by what caused them, because the cause drives the treatment. The four most common types each have a fairly distinct look and typical location.
Pressure ulcers
Also called bedsores or pressure sores, these form where bone presses skin against a surface for a long time. Common spots are the tailbone, heels, hips, elbows, and back of the head. They tend to start as a red or discolored patch and can progress to an open crater. Pressure ulcers are staged from 1 to 4 based on depth, with stage 4 reaching muscle or bone. People who are immobile, use a wheelchair, or are hospitalized for long periods are at highest risk.
Venous ulcers
These come from poor blood flow back up the legs, usually because veins in the leg are damaged. They most often appear on the inner ankle or lower leg. The skin around them is often discolored brown or reddish, swollen, and itchy. Venous ulcers are the most common type of leg ulcer in many clinical settings, and they tend to weep fluid.
Arterial ulcers
These result from poor blood flow to the leg because arteries are narrowed or blocked. They often show up on the toes, the outer ankle, or pressure points on the foot. They tend to be deep, with pale or black tissue and a punched-out edge. The skin around them may look shiny and cool, and the pain often gets worse when the leg is raised or at rest.
Neuropathic (diabetic) ulcers
These happen when nerve damage removes the sensation of pain, so a person does not feel a blister, a cut, or repeated pressure. They most often form on the bottom of the foot at pressure points. Because feeling is reduced, they can grow large before anyone notices. Diabetes is the most common cause, which is why foot checks are a routine part of diabetes care.
Other types exist, including ulcers caused by prolonged moisture, infections, inflammatory conditions, or certain medications. A wound that does not fit a clear pattern should be evaluated by a clinician rather than self-diagnosed.
How Can You Tell the Types Apart?
The location, the surrounding skin, and the pattern of pain often point to the type before any testing. This is a general guide, not a diagnosis — a clinician confirms the cause with an exam and, when needed, tests such as blood flow studies.
| Feature | Pressure ulcer | Venous ulcer | Arterial ulcer | Diabetic (neuropathic) ulcer |
|---|---|---|---|---|
| Usual location | Tailbone, heels, hips | Inner ankle, lower leg | Toes, outer ankle, foot | Bottom of the foot |
| Wound edges | Varies by stage | Irregular, shallow | Punched-out, deep | Callused rim, often painless |
| Surrounding skin | Red or discolored | Brown, swollen, itchy | Pale, shiny, cool | Thick callus, dry skin |
| Typical pain | Present | Mild to moderate | Often severe, worse at rest | Often reduced or absent |
| Drainage | Varies | Often weepy | Minimal | Varies |
These patterns overlap, and some people have more than one type at once. For example, a person with diabetes can have both nerve damage and poor circulation, so a foot wound may have features of two types. That overlap is one reason a professional assessment matters.
What Are the Warning Signs of an Infected Ulcer?
Infection is the complication that turns a manageable ulcer into an emergency. The signs are usually visible and get worse rather than better.
- Increasing redness, warmth, or swelling around the wound
- Thick, yellow, green, or foul-smelling drainage
- Pain that gets worse instead of better
- Red streaks spreading from the wound
- Fever, chills, or feeling generally unwell
- The wound getting larger or deeper despite care
Fever or red streaks moving up a limb are reasons to seek care right away. In people with diabetes or poor circulation, infection can spread quickly and quietly. Any ulcer that is not improving, or is getting worse, needs medical evaluation.
When Should You See a Doctor About a Skin Ulcer?
Any open sore that has not started to heal within a couple of weeks should be checked. That is a general rule of thumb, not a hard cutoff, and a wound that is clearly worsening should be seen sooner.
See a clinician promptly if you have:
- A wound with black or dead tissue
- Signs of infection such as fever, pus, or spreading redness
- Diabetes, poor circulation, or nerve damage in the feet or legs
- A wound that is deep, bleeding, or exposing deeper tissue
- Pain that is severe or getting worse
People with diabetes should not try to treat a foot wound at home. Reduced sensation can hide how serious a wound is, and delayed care is a common reason foot ulcers lead to worse outcomes. Regular foot checks are part of standard diabetes care for exactly this reason.
How Are Skin Ulcers Treated?
Treatment targets the cause, not just the wound. A venous ulcer will not heal well without addressing the vein problem. A pressure ulcer will keep returning without relieving the pressure. An arterial ulcer may need procedures to restore blood flow.
General wound care often includes cleaning, removing dead tissue, keeping the wound moist with appropriate dressings, and managing infection when present. Beyond that, treatment is cause-specific:
- Pressure ulcers: Repositioning, special support surfaces, and pressure-relieving devices.
- Venous ulcers: Compression therapy, which is a mainstay for this type, along with elevation and wound care.
- Arterial ulcers: Improving blood flow, sometimes with procedures or surgery, plus careful wound care.
- Diabetic ulcers: Offloading pressure from the foot, blood sugar control, and treatment of any infection.
Compression is helpful for venous ulcers but can be harmful in arterial disease, where blood flow is already limited. That is why the type has to be confirmed before treatment. The evidence for compression in venous ulcers is strong; the evidence for any single dressing product “healing” an ulcer on its own is much weaker. Dressings support healing, but they do not fix the underlying cause.
No single treatment works for every ulcer, and recovery timelines vary widely based on the cause, the person’s overall health, and how well the cause is controlled. A clinician tailors the plan to the individual.
Can Skin Ulcers Be Prevented?
Many ulcers can be prevented, especially pressure and diabetic ulcers, because the risk factors are known and often manageable.
- Check feet daily if you have diabetes, looking for cuts, blisters, redness, or swelling.
- Change position regularly if you are immobile or use a wheelchair.
- Use support surfaces and padding to reduce pressure on bony areas.
- Keep skin clean and moisturized, and manage moisture from sweat or incontinence.
- Control blood sugar if you have diabetes.
- Stay active within your limits to support circulation.
- Wear properly fitted shoes and check them for objects before putting them on.
Prevention works best when it is consistent. A single missed check on a numb foot can let a small problem grow. For people at high risk, routine professional foot and skin exams are part of standard care.
Frequently Asked Questions
What does a skin ulcer look like at first?
It often starts as a red or discolored patch, a small blister, or a shallow break in the skin that does not heal. As it progresses, it can become an open crater with clear edges.
How do I know if a skin ulcer is infected?
Signs include increasing redness, warmth, swelling, thick or foul-smelling drainage, worsening pain, and sometimes fever or red streaks. Any of these should prompt a medical evaluation.
What is the most common type of skin ulcer?
Venous ulcers are among the most common leg ulcers, while pressure ulcers are common in people who are immobile. The most frequent type depends on the population and setting.
When should a skin ulcer be seen by a doctor?
Any ulcer that has not begun to heal within a couple of weeks, or that is getting worse, should be checked. People with diabetes or poor circulation should seek care sooner.
