Scab (Skin Wound) – Formation Process, Causes, Pictures, Care

Scabs are a common occurrence in life that forms when we have everyday injuries, like after a fall or cutting our finger with a knife. It is a temporary crust that helps with wound healing. While scabs are not usually a sign of any serious disease and a good sign of wound healing, problems can arise if it is removed prematurely.

What is a scab?

A scab is hard protective tissue that form on the skin surface at a site of damage. It starts with a blood clot, which forms when components in the bloodstream are activated at deposited where a blood vessel is broken. Once this break is plugged, wound healing causes the clot to eventually becomes a hard protective crust on the surface known as a scab. The formation of a scab is part of the healing process as skin grows over the wound.

Scabs form rapidly with most injuries which are minor. Tissue regeneration occurs rapidly and gradually pushes out the scab. Eventually the scab falls off or may be picked out. If the underlying tissue has closed the break then a new scab will not form. However, if the wound has not healed sufficiently and picking the scab leads to bleeding again, then a new scab forms.

How do scabs form?

In order to understand scab formation, it is important to first know more about blood clotting (coagulation). When a blood vessel is broken, the normally inactive clotting factors circulating in the bloodstream are activated. Components in the blood like platelets stick to the area along with red blood cells and this forms a clot. It is accompanied by fibrin strands which forms when thrombin converts fibrinogen into fibrin.

These fibrin strands provide a mesh for more blood cells to adhere to the injured area. The clot forms very fast to ensure that blood loss is minimal by physically plugging in the break. White blood cells are also recruited to the area and provides additional immune defenses to prevent any invading organisms from causing an infection. The clot eventually contracts to draw the broken ends together and allow for more effective wound healing.

With time the clot hardens and becomes a protective crust which is referred to as a scab.

Scabs vs Scars

Scabs are not the same as scars. A scab is a temporary crust that forms to protect a damaged area of the skin until the tissue heals and new skin grows in its place. The scab will then fall off although in many instances a person may pick at the scab and physically removed it.

A scar on the other hand is a permanent deposition of fibrous tissue to replace damaged or lost skin that cannot be repaired or replaced. Scabs may initially form at the site of a scar but if the injury to area is very severe then normal skin growth is not possible. Eventually the scab may fall off and fibrous tissue grows at the site to form the scar.

Pictures of Scabs



Causes of Scabs

Any condition that compromises the integrity of the skin and causes a break in superficial blood vessels will lead to scab formation. It can be as minor as a small cut (laceration) to skin diseases like psoriasis and even large wounds. Scabs are less likely to form in large wounds where either end of the injured tissue is separated and the wound is deep. The latter usually requires stitches to bring the opposite ends close together thereby helping wound healing. This may lead to a scab and a scar may form.


For most people, injury is by far the most common cause of scabs. Injuries arise from accidents like cutting the skin with a knife, falls, insect bites, contact sports, assaults and burns. The development of scab depends on the severity of an injury an whether there is a break in the skin and a blood vessel. However, even without impact, bleeding may occur with actions like vigorous scratching of the skin.

Skin Diseases

Any condition that compromises the integrity of the skin can contribute to scab formation, especially where the underlying blood vessels are broken. This is seen with a host of skin conditions such as atopic dermatitis, contact dermatitis, skin infections, chickenpox, herpes simplex virus that causes cold sores, psoriasis and other skin diseases. In itchy skin conditions, scratching can also lead to scab development.


There are some rare conditions where bleeding may occur with very minor trauma, and seem to appear almost spontaneously. Therefore scabs form on widespread parts of the body and this occurs on a continuous basis as new breaks in the skin arise.

How to care for a scab?

Although a scab signals good wound healing and usually the lack of complications like an infection, the same principles of wound care for open wounds can be applied to some extent. However, by the time a scab is present it is usually indicative that the body’s repair and defense mechanisms are functioning optimally and no significant intervention is required.

  • Never pick a scab shortly after it forms. Wound healing is occurring underneath the scab and depending on the severity of the injury, this can take a few days to 1 to 2 weeks. Removing a scab can interrupt this process.
  • Do not scratch the area even if it is itchy. Scratching may prematurely remove a scab, trigger bleeding again and even open the are to an infection.
  • Protect the area from further injury. Although a scab is a hard crust, the skin integrity has not been restored to a normal level. Further injury can remove the scab and interrupt normal wound healing.
  • Keep the area clean. This means washing the area gently with an antibacterial soap. In the event that the scab is prematurely removed, good hygiene will prevent the damaged area from becoming infected.
  • Use an antibacterial cream when the injury arises and continue it for a few days even after the scab forms. While this is not always necessary once the scab is present, it can reduce the risk of infections should the scab be disturbed or removed.


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