What causes sores that won't heal? Understanding chronic wounds

September 26, 2025 •

4 min read

According to the National Institutes of Health, over 6.5 million Americans are affected by chronic, non-healing wounds. When faced with a stubborn injury, many people wonder exactly what causes sores that won't heal and why they defy the body's natural mending process.

Quick Summary

Chronic wounds, or sores that do not heal, are often caused by underlying medical conditions that interfere with the body's natural healing process, including poor circulation, diabetes, nutritional deficiencies, and infections. Understanding these root causes is the first step toward effective treatment and preventing further complications.

Key Points

Underlying Health Conditions: Chronic sores are often caused by conditions like diabetes, vascular disease, or a weakened immune system that disrupt the body's healing process.
Poor Circulation is a Major Factor: Inadequate blood flow, due to conditions such as venous insufficiency or peripheral artery disease, prevents oxygen and nutrients from reaching the wound site.
Infection Can Stall Healing: Bacterial infections in an open wound can divert the body's healing resources, prolonging the inflammatory phase and preventing tissue repair.
Repeated Trauma is Detrimental: Constant pressure or friction, as seen with pressure ulcers (bedsores), can continuously damage new tissue and prevent a wound from closing.
Nutrition and Lifestyle Matter: Nutritional deficiencies, especially lacking protein, vitamins, and zinc, can impair healing, as can habits like smoking which constrict blood vessels.
Professional Diagnosis is Key: If a sore doesn't heal within a few weeks, it is essential to see a doctor for a proper diagnosis and treatment plan, which may involve specialized wound care.
Early Intervention is Crucial: Ignoring a non-healing wound can lead to serious complications, including deep tissue infections and further health problems.

The complex process of wound healing

To understand why a sore might not heal, it's helpful to first understand the normal stages of wound healing. This complex biological process is divided into four main phases: hemostasis, inflammation, proliferation, and maturation. In hemostasis, blood clots to stop the bleeding. Inflammation follows, where the body sends white blood cells to clean the wound and fight off infection. The proliferative phase involves rebuilding the wound with new tissue and blood vessels. Finally, maturation sees the new tissue strengthening and reorganizing. A sore that won't heal, known as a chronic wound, occurs when one or more of these phases are disrupted or prolonged.

Common underlying medical conditions

Many factors can interrupt the healing cascade. The most significant are often chronic health conditions that compromise the body's ability to repair itself.

Diabetes: High blood sugar levels can damage blood vessels and nerves, leading to poor circulation and a weakened immune system. This impairs the delivery of oxygen and nutrients to the wound, slowing healing and increasing the risk of infection. Diabetic foot ulcers are a common example of this complication.
Vascular disease: Conditions that affect blood flow, such as venous insufficiency or peripheral artery disease (PAD), are major culprits. Poor circulation prevents essential nutrients and oxygen from reaching the wound site, while also hindering the removal of waste products. This can lead to the formation of venous or arterial ulcers, particularly on the legs and feet.
Compromised immune system: Autoimmune diseases, HIV/AIDS, or immunosuppressive medications (like corticosteroids) can weaken the body's ability to fight off bacteria and control inflammation, making it harder to heal.

Factors in the wound's environment

Beyond internal health, the immediate environment of the sore plays a crucial role in its healing potential.

Infection: A bacterial infection is one of the most common reasons for a wound not healing. Bacteria can thrive in an open wound, diverting the body's resources toward fighting the infection rather than repairing tissue. Signs of infection include increased pain, redness, swelling, pus, and a foul odor.
Pressure or trauma: Repetitive pressure, friction, or injury to a wound site can continuously damage new tissue and prevent healing. This is the primary cause of pressure ulcers, or bedsores, which are a major concern for immobile individuals.
Dead tissue (Necrosis): The presence of dead or necrotic tissue in a wound bed can act as a barrier to healing. It can also be a breeding ground for bacteria, necessitating its removal (debridement) for healing to progress.

Lifestyle and nutritional influences

Individual habits and diet can also have a profound impact on the body's healing capabilities.

Poor nutrition: The body requires specific nutrients to heal effectively, including protein, vitamins (especially C and A), and minerals (like zinc). A deficiency in any of these can significantly impair the healing process. Protein is the building block for new tissue, and a lack of it can stall repair.
Smoking: Nicotine constricts blood vessels, reducing blood flow and oxygen delivery to the wound. Smoking also impairs the function of immune cells, making the body more vulnerable to infection.
Obesity: Excess weight can place additional pressure on the skin, particularly in areas like the legs, and can also lead to issues with poor circulation.

Comparing types of chronic wounds

Understanding the specific type of non-healing wound can guide the correct treatment strategy. The table below compares some common types of chronic ulcers.


Feature	Diabetic Foot Ulcers	Venous Leg Ulcers	Pressure Ulcers	Arterial Ulcers
Primary Cause	Nerve damage (neuropathy) and poor circulation from diabetes.	High pressure in leg veins due to venous insufficiency.	Sustained pressure on skin over bony areas.	Blocked arteries causing poor blood flow to extremities.
Appearance	Often deep, punched-out appearance. Callus formation may surround the wound.	Shallow, irregularly shaped, with a red base and moist fluid (exudate).	Circular, with a crater-like look. Varies by stage of severity.	Punched-out appearance, usually with a pale base and dry look.
Location	Typically on the soles of feet, toes, or balls of the feet.	Inner ankle area (medial malleolus) is a common location.	Heels, ankles, hips, and tailbone.	Feet, toes, and ankles.
Other Signs	Loss of sensation, burning, or tingling in the feet.	Swelling (edema), skin discoloration (staining), and thickened skin.	Pain, redness, or discolored skin. Blisters may form.	Diminished or absent pulses in the foot, shiny skin, hair loss.

Seeking professional guidance

If you have a sore that won't heal within a few weeks, it is crucial to consult a healthcare professional. They can properly diagnose the underlying cause and create an appropriate treatment plan. This may include specialized wound care, management of underlying conditions, and lifestyle adjustments. Never ignore a chronic wound, as it can lead to more serious complications, including deep tissue infections and even amputation.

For more detailed information on specific types of ulcers and their treatment, consult resources from a reputable organization such as the American Podiatric Medical Association. Early intervention is the key to preventing the progression of chronic wounds and promoting a return to health.

Conclusion: addressing the root problem

In conclusion, a sore that won't heal is not a minor inconvenience but a clear sign that something is interfering with the body's natural repair process. Whether it's an underlying systemic condition like diabetes or vascular disease, a localized issue like infection or pressure, or a lifestyle factor such as smoking or poor nutrition, identifying and addressing the root cause is paramount. By taking persistent sores seriously and seeking timely medical advice, individuals can navigate the complexities of chronic wounds and set a course toward proper healing and better health.

Frequently Asked Questions

A wound is generally considered non-healing or chronic if it fails to show significant signs of improvement within four to six weeks, or doesn't fully heal within eight weeks, despite proper care. This is a sign that an underlying issue is preventing the normal healing process.

While diabetes is a major risk factor for non-healing wounds, it does not always cause them. However, high blood sugar levels can significantly impair circulation and nerve function, making diabetic individuals more susceptible to chronic sores, especially foot ulcers.

The first step is to see a healthcare professional for an accurate diagnosis. In the meantime, ensure the wound is kept clean, covered with a sterile dressing, and protected from further injury. Do not attempt to self-treat with unproven remedies.

Yes, poor nutrition is a significant factor. The body requires specific nutrients, including protein, vitamins C and A, and zinc, to effectively rebuild tissue. A diet lacking in these essential components can seriously impair or stall the healing process.

Signs of an infected wound include increased redness, swelling, warmth, and pain. You may also notice pus or a foul odor. If you experience these symptoms, especially if accompanied by a fever, you should seek immediate medical attention.

Yes, constant pressure on a specific area of the skin can restrict blood flow and cause a sore, known as a pressure ulcer or bedsore. The continued pressure prevents the wound from healing, making it a persistent problem for individuals with limited mobility.

Yes, smoking is a significant factor. Nicotine constricts blood vessels, which reduces the amount of oxygen and nutrients delivered to the wound. This can severely slow down or completely stop the healing process.