A skin ulcer is an open wound in the skin that fails to heal through the normal repair process, often persisting for weeks, months, or even years. Unlike a cut or scrape that closes on its own, an ulcer typically signals an underlying problem with blood flow, nerve function, or sustained pressure on the tissue. The vast majority fall into a handful of categories, with venous disease, arterial disease, diabetes, and immobility accounting for the bulk of cases. But the biology of why these wounds stall is more interesting and more treatable than many people realize.
Why a Wound Becomes an Ulcer
Normal wound healing follows a predictable sequence: bleeding stops, inflammation clears debris and bacteria, new tissue fills the gap, and the skin remodels itself over time. A skin ulcer develops when something disrupts that sequence and the wound gets stuck, usually in the inflammatory phase. The tissue keeps breaking down faster than the body can rebuild it.
One major reason chronic ulcers stall is that the wound fluid itself becomes destructive. Research has shown that fluid from chronic leg ulcers contains dramatically elevated levels of enzymes called metalloproteinases, roughly five to ten times higher than levels found in healing surgical wounds. These enzymes, which normally help remodel tissue in a controlled way, instead chew through new tissue as fast as the body lays it down, creating a cycle of chronic tissue turnover and failed closure.1Journal of Investigative Dermatology. Wound Fluid from Chronic Leg Ulcers Contains Elevated Levels of Metalloproteinases MMP-2 and MMP-9
Oxygen supply matters too. Healthy wound healing depends on the body’s ability to sense low oxygen in damaged tissue and ramp up a repair response. When that sensing mechanism breaks down, the tissue stays starved of oxygen without triggering the compensatory growth of new blood vessels and repair cells. This chronic oxygen deprivation has been directly linked to the formation of nonhealing ulcers.2PubMed Central. The Role of Hypoxia-Inducible Factor in Wound Healing
The Main Types of Skin Ulcers
While many conditions can produce a skin ulcer, most cases trace back to one of four causes. Recognizing which type you’re dealing with matters because the treatment strategies differ sharply.
Venous Leg Ulcers
These are the most common type of chronic leg ulcer. They develop when the valves inside leg veins stop working properly, allowing blood to flow backward and pool in the lower legs instead of returning efficiently to the heart. That pooling drives up pressure inside the veins, which triggers a cascade of swelling, inflammation, skin changes, and oxygen deprivation in the surrounding tissue. Over time, the skin becomes fragile and discolored, a condition sometimes called lipodermatosclerosis, and even a minor bump or scratch can open a wound that refuses to close.3PubMed Central. Chronic venous insufficiency and venous leg ulcers: Aetiology, on the pathophysiology-based treatment Venous ulcers typically appear around the inner ankle, tend to be shallow and irregularly shaped, and often weep fluid.
Arterial Ulcers
Where venous ulcers come from blood not leaving the legs well enough, arterial ulcers come from blood not arriving well enough. Cholesterol plaques and other debris narrow the arteries feeding the limb, sometimes to the point where the tissue can’t get enough oxygen and nutrients even at rest. This advanced state of artery disease leads to skin breakdown and tissue death, typically on the toes, feet, or lower shins.4Advances in Skin & Wound Care. Arterial Disease Ulcers, Part 1: Clinical Diagnosis and Investigation Arterial ulcers look different from venous ones: they tend to have sharply defined edges, a pale or gray wound bed, and they hurt, especially at night or when the legs are elevated. The surrounding skin is often cool and hairless.
Diabetic Foot Ulcers
Diabetes attacks wound healing from multiple directions at once. Nerve damage (neuropathy) means you may not feel a blister, cut, or pressure point on your foot. Structural changes in the bones and tendons alter how weight distributes across the sole. And artery disease, which is especially common in people with diabetes, restricts blood flow on top of everything else. Up to half of people with diabetes who develop a foot ulcer also have concurrent artery disease, which significantly raises the risk of losing the limb.5PubMed. Guidelines on diagnosis, prognosis, and management of peripheral artery disease in patients with foot ulcers and diabetes (IWGDF 2019 update) The combination of not feeling the injury and not being able to heal it makes diabetic foot ulcers one of the leading causes of non-traumatic amputations worldwide.6PubMed. The diabetic foot
Pressure Ulcers
Sometimes called bedsores or pressure injuries, these develop when sustained mechanical loading cuts off blood flow to the skin and underlying tissue. The classic scenario is someone confined to a bed or wheelchair who can’t shift position often enough. As blood flow drops under prolonged pressure, the tissue starves and begins to die. Shear forces, where layers of tissue slide against each other during repositioning, add further damage, though pressure itself is the dominant factor.7PubMed. The effect of pressure and shear on tissue viability of human skin in relation to the development of pressure ulcers: a systematic review Common sites include the sacrum, heels, hips, and the back of the head. Pressure ulcers can range from superficial redness to deep craters exposing muscle or bone.
The Biofilm Problem
One of the biggest obstacles to healing a chronic ulcer is something you can’t see with the naked eye. Bacteria in chronic wounds tend to organize themselves into biofilms: structured colonies encased in a slimy protective matrix that shields them from both the immune system and antibiotics. Biofilms are found in up to about 60% of chronic wounds, compared with roughly 6% of fresh wounds.8PubMed Central. Biofilms and Chronic Wounds: Pathogenesis and Treatment Options
The damage biofilms do goes beyond simple infection. They drive constant inflammation by activating immune cells that flood the wound with inflammatory signals, which in turn break down the structural proteins the body is trying to lay down as new tissue. The result is a wound locked in a self-perpetuating cycle: the biofilm provokes inflammation, the inflammation degrades healing tissue, and the damaged tissue provides a welcoming environment for the biofilm to persist. Standard courses of oral or topical antibiotics often fail to penetrate the protective matrix, which is why physical removal of the biofilm through debridement is usually the first step in breaking the cycle.
How Skin Ulcers Are Diagnosed
Most skin ulcers are recognizable on sight to an experienced clinician, but identifying the type and its underlying cause requires more than looking at the wound. The single most important question for a leg ulcer is whether the arteries are delivering enough blood, because this determines whether compression therapy, the cornerstone of venous ulcer treatment, is safe. Wrapping a leg with poor arterial supply can make things dramatically worse.
The standard screening tool is the ankle-brachial index, which compares blood pressure at the ankle with blood pressure in the arm using a handheld ultrasound probe. It’s quick, painless, and picks up artery disease with high accuracy: one study of patients with chronic leg ulcers found a sensitivity of about 85% and specificity of 97% compared with full arterial ultrasound imaging.9Journal des Maladies Vasculaires. Ease of use, feasibility and performance of ankle arm index measurement in patients with chronic leg ulcers: Study of 100 consecutive patients In older adults and people with stiff, calcified arteries (common in diabetes), the ankle reading can be falsely reassuring, so some clinicians also measure blood pressure at the toe, which is harder to falsify. Using both measurements together, followed by a Doppler ultrasound scan for borderline cases, is the approach recommended for older adults with leg ulcers.10PubMed. Evaluation of the ankle brachial index and toe brachial index for peripheral arterial disease diagnosis in patients over 70 years with lower limb ulcers
If the ulcer doesn’t look like it fits neatly into the venous, arterial, or diabetic categories, or if it fails to improve with appropriate treatment, a biopsy is typically the next step. This helps rule out less common causes, including autoimmune conditions and cancer.
Atypical Ulcers and Autoimmune Causes
Not every skin ulcer traces back to vascular disease or pressure. A small but important subset of ulcers is caused by the immune system itself. Pyoderma gangrenosum is the most well-known example: a painful, rapidly enlarging ulcer that often starts at the site of a minor skin injury and looks infected but isn’t responding to antibiotics. It’s driven by an overactive inflammatory response rather than by bacteria. Skin samples from affected patients show dramatically elevated levels of inflammatory signaling molecules compared with healthy skin, and researchers have identified mutations in several genes involved in regulating inflammation.11PubMed. Autoinflammation in pyoderma gangrenosum and its syndromic form (pyoderma gangrenosum, acne and suppurative hidradenitis)
Pyoderma gangrenosum is frequently misdiagnosed as an infected wound, leading to repeated surgical debridement that actually makes it worse, because cutting into the skin can trigger new ulceration in someone with this condition (a phenomenon called pathergy). It often appears alongside inflammatory bowel disease, rheumatoid arthritis, or blood disorders. Treatment involves suppressing the immune response rather than fighting infection, which is why getting the diagnosis right is critical.
Other autoimmune and inflammatory conditions that can produce skin ulcers include vasculitis (inflammation of blood vessel walls), scleroderma, lupus, and calciphylaxis in people with kidney disease. When an ulcer appears in an unusual location, has atypical features, or simply won’t respond to standard wound care, these diagnoses deserve consideration.
Treatment Approaches
Treating a skin ulcer effectively means addressing both the wound itself and whatever caused it. A beautifully dressed venous ulcer will reopen if the underlying vein problem isn’t managed. A debrided diabetic foot ulcer will break down again if the patient keeps walking on it without proper offloading. The most common treatments fall into a few broad categories.
Compression for Venous Ulcers
Graduated compression, applied through bandages or stockings, is the most evidence-backed treatment for venous ulcers. It counteracts the high venous pressure that caused the problem in the first place, reducing swelling and improving blood return from the legs. Once a venous ulcer heals, continued use of compression stockings is the single most effective way to prevent it from coming back. Cochrane review data suggests that strong compression stockings roughly halve the risk of a venous ulcer recurring compared with no compression over six months.12Cochrane Database of Systematic Reviews. Compression for preventing recurrence of venous ulcers The catch is that lighter stockings, while easier to put on and more likely to be worn consistently, appear to allow more recurrences than stronger ones. Many clinicians find themselves navigating the trade-off between the strongest compression and the compression a patient will actually wear every day.
Debridement
Removing dead, damaged, or infected tissue from the wound bed is a foundational step in treating most chronic ulcers. Without debridement, biofilms and dead tissue block new cell growth and keep inflammation churning. Methods range from sharp debridement (using a scalpel or curette in a clinical setting) to enzymatic ointments and autolytic approaches where moist dressings help the body’s own enzymes soften dead tissue.
One of the more attention-grabbing methods is maggot debridement therapy, which uses sterile larvae of the green bottle fly placed onto the wound. The larvae selectively digest dead tissue while leaving healthy tissue alone, reduce bacterial load, and appear to stimulate the growth of new granulation tissue.13PubMed Central. Mechanisms of Maggot-Induced Wound Healing: What Do We Know, and Where Do We Go from Here? It sounds medieval, but the approach has been studied in modern clinical settings and has found a role particularly in diabetic foot ulcers and other chronic wounds where conventional debridement has fallen short.14PubMed Central. Surgical debridement and maggot debridement therapy can survive patient with diabetic foot ulcer after foot trauma: A case report
Negative Pressure Wound Therapy
Negative pressure wound therapy, sometimes called wound VAC (vacuum-assisted closure), involves placing a foam or gauze dressing into the wound, sealing it under an airtight film, and connecting it to a pump that applies gentle suction. The sustained negative pressure draws wound edges together, pulls out inflammatory fluid, stabilizes the wound environment, and stimulates the growth of new blood vessels and tissue at a microscopic level.15PubMed Central. Negative Pressure Wound Therapy: Mechanism of Action and Clinical Applications It’s particularly useful for large, deep, or surgically debrided ulcers that need to fill in a significant volume of tissue before they can close.
Skin Substitutes
For ulcers that resist conventional treatment, bioengineered skin substitutes offer another option. These are lab-grown products, derived from human, animal, or synthetic sources, that are placed directly onto a prepared wound bed. Rather than simply covering the wound, they act as scaffolds that encourage the patient’s own cells to migrate in and rebuild. Some versions also release growth factors and other signaling molecules that actively push healing forward.16PubMed. The role of skin substitutes in the management of chronic cutaneous wounds Bilayered skin substitutes, which mimic both the top and deeper layers of skin, have shown particular promise as add-ons to standard therapy for venous leg ulcers and full-thickness diabetic foot ulcers that haven’t responded to conventional care.17PubMed. Bilayered bioengineered skin substitute (Apligraf): a review of its use in the treatment of venous leg ulcers and diabetic foot ulcers
Hyperbaric Oxygen Therapy
Hyperbaric oxygen therapy involves breathing pure oxygen in a pressurized chamber, which dramatically increases the amount of oxygen dissolved in the blood and delivered to tissues. For diabetic foot ulcers, the evidence is encouraging: the treatment has been shown to boost the growth of new blood vessels, reduce inflammation, and enhance collagen production in wound tissue.18PubMed. Tissue-specific role of Nrf2 in the treatment of diabetic foot ulcers during hyperbaric oxygen therapy It also has antimicrobial effects, as many of the bacteria thriving in chronic wounds do poorly in high-oxygen environments. Hyperbaric therapy is typically reserved for wounds that have failed other treatments, partly because it requires repeated sessions in specialized facilities and is not widely accessible.
Nutrition and Wound Healing
One of the most underappreciated factors in ulcer healing is what the patient eats. Poor nutrition and insufficient dietary intake are well-documented risk factors for both developing pressure ulcers and failing to heal from them. Healing tissue has increased demands for energy, protein, zinc, and vitamins A, C, and E, along with amino acids like arginine and glutamine.19PubMed Central. Pressure Ulcer and Nutrition When those building blocks aren’t available, collagen production slows, immune function weakens, and tissue strength drops.
Protein deserves special mention. In one study of venous ulcer patients, protein deficiency was independently associated with wound enlargement over 12 weeks rather than healing, and the presence of systemic inflammation was linked to wound complications such as infection or hospitalization.20PubMed. Impact of protein deficiency on venous ulcer healing This is a practical finding that often gets overlooked: many people with chronic wounds are elderly, have limited appetites, or are managing other conditions that suppress dietary intake. A nutritional assessment should be part of any ulcer treatment plan, yet it frequently isn’t.
Research into specific supplements is still developing. One trial found that magnesium supplementation over 12 weeks improved ulcer size and inflammatory markers in patients with diabetic foot ulcers.21PubMed Central. Impact of nutrition on skin wound healing and aesthetic outcomes: A comprehensive narrative review That said, the ideal combination and dose of nutrients for wound healing remains unclear. The broader principle is well established: if you’re malnourished, your wounds will struggle to heal regardless of what dressings or therapies are applied.
When Ulcers Turn Dangerous
Beyond the obvious risks of infection and pain, chronic skin ulcers carry a complication that many people don’t know about. A wound that has been open for years can undergo malignant transformation, developing into an aggressive form of skin cancer known as a Marjolin’s ulcer. Despite the name, it is not a type of ulcer but a cancer, most often squamous cell carcinoma, that arises within the chronically inflamed and scarred tissue of a long-standing wound.22PubMed Central. Marjolin’s ulcer in chronic wounds – review of available literature
Marjolin’s ulcers are rare, but they tend to be more aggressive than typical skin cancers, with a higher rate of spread to lymph nodes and distant organs.23PubMed Central. Systematic Review of Modern Case Series of Squamous Cell Cancer Arising in a Chronic Ulcer (Marjolin’s Ulcer) of the Skin The average lag time between the original wound and cancer development is typically measured in decades, though shorter intervals have been documented. Warning signs include a sudden change in the ulcer’s appearance, rapid growth, raised or rolled edges, increased pain, or a foul-smelling discharge. Any chronic wound that changes character after a long period of stability deserves a biopsy.24PubMed Central. A Comprehensive Review on Marjolin’s Ulcers: Diagnosis and Treatment This is one reason why the goal with any chronic ulcer should always be healing it completely rather than simply managing it indefinitely.
The Psychological and Financial Toll
Living with a chronic wound affects far more than the skin. Chronic ulcers impose a substantial psychological, social, and financial burden on patients and healthcare systems alike.25PubMed Central. A Review of Chronic Wounds and Their Impact on Negative Affect, Cognition, and Quality of Life Pain, smell, leaking dressings, and restricted mobility can lead to social isolation, depression, anxiety, and difficulty sleeping. Many patients describe feeling embarrassed or ashamed of their wound, which limits their willingness to go out, exercise, or maintain relationships.
The financial costs are considerable as well. Chronic wound care involves frequent clinic visits, specialized dressings, medications, and sometimes hospital admissions. For venous ulcers, which can take months or more than a year to close and have high recurrence rates, the cumulative expense adds up quickly. In many healthcare systems, wound care consumes a disproportionate share of community nursing resources. These realities have pushed researchers toward technologies that could allow more wound monitoring to happen at home.
Smart Bandages and Emerging Technology
Traditional wound dressings are passive: they cover the wound and absorb fluid but provide no information about what’s happening underneath. A growing field of research is working to change that. So-called smart bandages integrate sensors that can monitor wound conditions such as temperature, moisture levels, and pH in real time. Some experimental designs also incorporate drug-delivery systems that release medications directly into the wound in response to detected changes, removing the need for a clinician to manually adjust treatment at every visit.26PubMed Central. Smart Bandages: The Future of Wound Care
The appeal is obvious for chronic ulcer patients who currently need frequent in-person wound assessments. A bandage that flags early signs of infection through a temperature spike or pH shift could prompt a clinic visit before the wound deteriorates rather than after. And automated drug release could maintain more consistent therapeutic levels than the feast-and-famine cycle of scheduled dressing changes. These technologies are still largely in the research phase, and questions remain about cost, durability, and how to integrate the data streams into clinical workflows. But for a patient population that may spend years cycling through dressing changes, even modest improvements in monitoring could translate into faster healing times and fewer complications.