Sores on the feet are breaks in the skin, lesions, or ulcerations that expose underlying tissue. Because the feet bear the body’s weight and are confined within footwear, they are highly susceptible to mechanical stress and injury. This pressure and friction, combined with poor circulation or underlying medical conditions, frequently compromises skin integrity. Understanding the distinct causes is essential for effective management and prevention.
Sores Caused by External Pressure and Friction
Mechanical forces are a common reason for the skin on the feet to break down, typically resulting from acute or chronic trauma. Blisters are the most immediate form of this injury, forming when shear forces between the skin layers cause a separation, allowing fluid to collect beneath the epidermis. This is usually due to ill-fitting shoes or a prolonged period of intense friction.
A more chronic form of mechanical stress leads to the development of corns and calluses, which are thickened layers of skin intended to protect the area from repeated pressure. If the source of pressure is not removed, the callus can become overly dense and push inward, causing tissue damage beneath the hardened surface. When this underlying tissue breaks down, a pressure ulcer can form, even in otherwise healthy skin.
Pressure ulcers are injuries to the skin and underlying tissue caused by sustained pressure that restricts blood flow. The heels, ankles, and the ball of the foot are particularly vulnerable bony areas where external force compresses the tissue against a hard surface. If the pressure is not relieved, the lack of oxygen and nutrients leads to tissue death and the formation of an open wound.
Sores Resulting from Infections
Pathogens that breach the skin barrier or thrive in the foot’s warm, moist environment can cause sores or lead to secondary infections. Fungal infections, such as Athlete’s foot (tinea pedis), often begin with scaling and itching between the toes. This condition can lead to painful fissures, which are small cracks in the skin barrier that become open sores.
Ulcerative Athlete’s foot involves deep breaks in the skin, serving as an entry point for bacteria. Bacterial infections can turn a minor cut or fissure into a rapidly worsening sore, potentially progressing to cellulitis, a deep skin infection characterized by spreading redness, warmth, and swelling. If the infection localizes, it can form an abscess, a tender, pus-filled pocket beneath the skin surface.
Viral agents are another source of lesions on the foot, most commonly exemplified by plantar warts. These growths are caused by the Human Papillomavirus (HPV) and typically appear on the sole of the foot, often covered by a thick callus due to the pressure of walking. Although not ulcers themselves, the continuous pressure on the wart can cause it to become extremely painful and occasionally break down, leading to a small, open sore.
Sores Linked to Underlying Systemic Health Issues
Certain chronic diseases impair the body’s ability to maintain skin integrity and heal minor injuries, making them the most significant cause of persistent foot sores. Diabetes mellitus is the leading systemic cause, primarily through two related mechanisms: diabetic neuropathy and peripheral arterial disease.
Diabetic neuropathy is nerve damage that frequently affects the feet, causing a loss of protective sensation. A person with neuropathy may not feel a small cut, blister, or the constant pressure from a poorly fitting shoe, allowing a minor injury to progress into a full-blown ulcer without notice. This lack of pain perception is a major reason why diabetic foot ulcers can become large and severely infected before they are detected.
Peripheral arterial disease (PAD) is a circulatory issue where arteries supplying blood to the lower extremities become narrowed or blocked by plaque buildup. This reduces the flow of oxygen and nutrient-rich blood to the foot tissues, significantly slowing healing. Ulcers caused by poor blood flow (ischemic ulcers) are typically painful, appear on the tips of the toes or pressure points, and struggle to heal due to inadequate circulation.
Vascular issues not related to diabetes also contribute to foot sores, particularly venous stasis ulcers. These ulcers are caused by chronic venous insufficiency, a condition where faulty valves in the leg veins allow blood to pool instead of returning efficiently to the heart. The resulting fluid buildup and pressure in the lower leg cause the skin to become fragile and poorly nourished, leading to breakdown and ulcer formation, most commonly around the ankles.
Arterial ulcers are usually deep, have a “punched-out” appearance, and are found on the toes or heel. Venous ulcers are typically shallow, irregularly shaped, and surrounded by discolored, thickened skin. These systemic issues demand specialized medical management because a small sore can quickly lead to deep infection or tissue death if the underlying circulatory or neurological problem is not addressed.
Sores from Inflammatory Skin Disorders
Sores on the feet can also arise from internal inflammatory processes driven by the immune system, rather than from external trauma or infection. These conditions represent a breakdown of the skin due to an underlying chronic skin disorder.
One example is severe contact dermatitis, an inflammatory reaction that occurs when the skin comes into contact with an irritant or allergen, such as chemicals in shoe materials or socks. This can result in intensely itchy, red patches that, when scratched or left untreated, develop into weeping, crusted, or open lesions.
Eczema, particularly dyshidrotic eczema, frequently affects the soles of the feet, causing the sudden appearance of deep-seated, small, and itchy blisters. These blisters eventually dry, leading to peeling, scaling, and painful cracking or fissuring of the skin. Psoriasis, an autoimmune condition, can also manifest on the feet with thick, silvery scales on red plaques that can crack and bleed, creating open wounds.