The appearance of dark or black discoloration on the heel can be an alarming symptom. This change in skin color results from underlying processes that range from simple mechanical issues to serious medical conditions. Understanding the origin of the black color is the first step in determining the severity, as it may be caused by pooled blood from trauma, tissue death due to lack of oxygen, or the accumulation of pigment from a disease process. Readers should seek professional evaluation to accurately diagnose the source of the discoloration.
Bruising from Impact or Friction
The most common causes for black discoloration on the heel relate to mechanical forces, either a single, acute impact or repetitive friction. A subdermal hematoma, which is the medical term for a deep bruise, occurs when trauma, such as stepping hard on an object, ruptures blood vessels beneath the skin. The blood pools under the skin, creating a swollen, tender area that appears dark purple or black as the body begins to reabsorb the blood. This trauma-induced discoloration is typically painful and resolves gradually over one to three weeks.
Another frequent cause, especially in athletes, is known as Talon Noir, or “Black Heel.” This condition is characterized by superficial, painless, speckled black or dark blue spots usually found on the back or sides of the heel. Talon Noir results from repetitive, lateral shearing forces that cause micro-trauma to the delicate capillaries in the papillary dermis.
The damaged capillaries leak tiny amounts of blood into the outermost layer of the skin, the stratum corneum, creating small hemorrhagic spots called calcaneal petechiae. Because this blood is trapped in the layer of dead skin cells, it remains visible until the skin naturally sheds. Talon Noir is benign and typically clears up on its own once the repetitive friction, such as running or playing sports that involve sudden stops, is stopped.
Discoloration Related to Blood Flow Issues
Black discoloration can signal a severe medical problem when it results from a lack of adequate blood flow to the heel tissue. Peripheral Artery Disease (PAD) is a condition where fatty deposits, or plaque, build up in the arteries, severely restricting the supply of oxygen-rich blood to the extremities. When PAD progresses to an advanced stage, it is termed Critical Limb Ischemia (CLI), a state of severe compromise that can manifest as persistent and intense pain even at rest.
Without sufficient oxygen and nutrients, the tissue begins to die, a process called necrosis, which results in the skin turning dark blue, purple, and eventually black. This black tissue is known as dry gangrene, a complication that commonly affects the toes, feet, and heels due to their distance from the heart. Unlike a bruise, this discoloration is often accompanied by other symptoms that indicate a true emergency, such as persistent coldness, numbness, or a weak pulse in the foot.
The pain associated with CLI is often described as a burning or aching sensation in the foot that worsens at night or when the patient is lying flat. This pain is temporarily relieved by dangling the leg over the side of a bed to allow gravity to assist blood flow. Non-healing wounds or ulcers on the heel, which are also a consequence of poor circulation, can become infected, leading to wet gangrene, a condition characterized by pus, foul odor, and rapid tissue destruction.
Other Potential Skin-Related Causes
Causes for black heel discoloration that fall outside of trauma or chronic circulatory failure include serious dermatological and systemic issues. A rare but aggressive form of skin cancer, Acral Lentiginous Melanoma (ALM), can appear on the soles or heels and may be mistaken for a simple bruise. This melanoma typically presents as a flat lesion with irregular borders and varied colors, including black, gray, or brown.
ALM is not caused by sun exposure and its appearance, especially on the heel, necessitates careful observation for any changes in size, shape, or color. Another serious cause is a rapidly progressing soft tissue infection, such as necrotizing cellulitis or fasciitis, which causes tissue death. This infection can quickly cause the skin to change from red and swollen to a dark, mottled, or black color.
Systemic conditions or drug reactions can also cause hyperpigmentation that appears black or dark on the heel. Certain medications, including minocycline (an antibiotic) and some antimalarials, can cause drug-induced hyperpigmentation, resulting in a slate-gray or blue-black discoloration due to the deposition of drug metabolites in the skin. Additionally, a Fixed Drug Eruption, a recurring reaction to a medication like an NSAID, can leave a dark, post-inflammatory spot on the foot that reappears upon re-exposure to the drug.
When Immediate Medical Attention is Necessary
The presence of black discoloration on the heel, when combined with specific accompanying symptoms, requires immediate medical evaluation. Seek emergency care if the discoloration is accompanied by sudden, severe, and unrelenting pain that is disproportionate to any visible injury. This can be a sign of acute arterial blockage or a rapidly progressing infection.
Other red flags include the foot or lower leg feeling cold to the touch, a loss of sensation, or a spreading numbness. Signs of a severe infection, such as fever, chills, rapid spreading redness, or the presence of pus or a foul-smelling discharge from the area, also warrant an urgent visit. Any discoloration that rapidly changes or expands in size over a short period should be considered an emergency.
A non-urgent medical appointment is appropriate if the discoloration is painless but does not fade or resolve within two weeks, which is the typical timeframe for a simple bruise. Likewise, any suspicious spot, especially one that has irregular borders or changes in size or shape over time, needs to be checked to rule out malignancy such as melanoma. Consulting a healthcare provider for any persistent or concerning skin change is the safest course of action.