Eschar is a piece of dead, devitalized tissue, or necrosis, that forms over a deep injury. It indicates a wound extending through multiple layers of skin, often reaching full-thickness levels. Unlike a simple scab, eschar consists of non-viable tissue that has died due to severe damage or lack of blood flow. Its presence makes it impossible to fully assess the injury underneath, which is why it requires significant attention in wound evaluation.
The Defining Visual Characteristics
Eschar typically presents as a dark covering, dramatically different in appearance and texture from the surrounding healthy skin. The coloration is usually deep, commonly described as black, dark brown, or occasionally grayish-black. This dark appearance results from the death and dehydration of the tissue, which concentrates the non-viable material.
The texture is notably firm and dry, often likened to hard leather or a crusty material. It feels rigid to the touch and may appear elevated or slightly depressed, depending on the wound’s depth.
A defining feature is its strong adherence to the underlying viable tissue, creating a clear, visible line of demarcation. The margins are usually well-defined, sometimes appearing slightly rolled or raised, emphasizing the boundary between the necrotic area and the surrounding healthy epidermis.
While typically hard, the tissue may sometimes present as soft, boggy, or fluctuant. This occurs if fluid or infection is trapped beneath the hard outer surface.
How Underlying Causes Alter Its Appearance
The specific visual presentation of eschar is significantly influenced by the original cause of the tissue damage, leading to variations in thickness and overall form.
Burn Eschar
In severe, full-thickness burns, the resulting eschar is often extremely thick, intensely black, and remarkably hard. This burn eschar frequently resembles charred material and can feel as rigid as the sole of a shoe, reflecting the extreme heat destruction of the collagen and dermal structures.
Pressure Injury Eschar
Eschar developing in advanced pressure injuries, such as those over bony prominences, often appears dark brown or grayish-black. While the surface may be dry, this type of eschar can be thinner and may hide a wetter layer underneath if the wound is deep and potentially infected. The presence of underlying moisture signals a compromised or unstable environment beneath the surface.
Infectious Eschar (Tache Noire)
A distinct form is the infectious eschar, often referred to as a tache noire, which is French for “black spot.” This lesion is commonly associated with rickettsial infections transmitted by ticks. It is typically smaller, measuring 0.5 to 3.0 centimeters in diameter, and presents as a central, black, crusty ulceration. The tache noire is characteristic because it is frequently surrounded by a noticeable annular red halo, indicating inflammation at the periphery.
The Role and Natural Progression of Eschar
Eschar serves a temporary biological function in the body’s initial response to a deep wound. The hard, desiccated tissue acts as a natural biological dressing, providing a physical barrier against the external environment. This protective layer helps prevent bacteria and contaminants from entering the wound bed, reducing the immediate risk of infection.
It also helps minimize fluid loss from the deeper layers, which is relevant in extensive injuries like severe burns. This protective role is why a dry, intact eschar on certain sites may be intentionally left in place by healthcare professionals.
As healing progresses, the body naturally attempts to separate the non-viable eschar from the viable tissue below through autolytic debridement. Enzymes begin to dissolve the connection between the dead and living layers, causing the eschar to soften and lift at the edges. This process eventually leads to the natural shedding, or sloughing, of the necrotic plaque.
If the eschar becomes unstable, wet, or indicates a high risk of infection, it must often be removed to allow for complete wound healing. Removing this non-viable tissue permits the wound to contract and the underlying tissue to regenerate without obstruction.