Scabs (Wound Crust) Formation, Causes and Scab Wound Care

What is a scab?

The term scab refers to the hard crust that forms over wounds on the skin as they heal. Scab formation is a part of the normal wound healing process. When an injury occurs, the first stages of wound healing are aimed at preventing blood loss through the formation of blood clots. These blood clots are formed by many different types of molecules present in the blood. The clots form at the sites of blood vessel leakage.

After the clots seal the blood vessels, tissue and skin regeneration processes begin. As the skin re-grows over the wound, the blood clot over the site of injury is transformed into a hard scab. Scab formation can be readily observed in case of minor injuries caused by cuts and falls during everyday activities. In these minor injuries, tissue regeneration and scab formation occur rapidly.

As the new skin and tissue re-grows over the wounded site, the scab is pushed out. Ultimately, the scab becomes loose enough to be picked off or falls off automatically. However, one should refrain from picking off a scab prematurely because it can cause further bleeding if the underlying wound hasn’t healed completely. That would delay wound healing and initiate the formation of a new scab.

How do scabs form?

Scab formation is a normal event during the process of wound healing. When an injury leads to the formation of a wound, bleeding occurs due to a break in the blood vessels that lie in the region of the injury. The tears in the blood vessels activate the clotting factors that are normal components of the blood. In intact blood vessels, these clotting factors circulate in the form of inactive precursors.

The clotting process triggered by the activation of the clotting factors leads to the formation of a blood clot at the site of blood vessel injury. The blood clot is formed by the accumulation of red blood cells, platelets, and fibrin protein at the site of injury. Fibrin protein normally circulates in the form of an inactive precursor called fibrinogen. The inactive fibrinogen is converted into active fibrin strands by thrombin, which is another factor in the clotting cascade.

Once activated, the strands of fibrin provide the meshwork to trap red blood cells, white blood cells and other components of the blood that form the clot. Clot formation is a rapid process that works to limit blood loss by quickly closing off the ruptured area in the blood vessel. Once clot formation is complete, other wound healing processes occur. During this stage, the clot itself contracts to allow tissue healing. As wound healing progresses, the contracted clot becomes hard and forms a crust over the site of the healing wound. This is the scab.

Read more on bleeding.

Scabs vs Scars

Although both scabs and scars form during the process of wound healing, they are entirely different structures. A scab is a temporary protective crust that forms over a healing wound. Once the wound heals, the scab either falls off on its own or can be picked off by hand. New skin formed during the process of wound healing lies just beneath the scab. Once the scab falls off or is removed, the new skin can be seen.

On the other hand, a scar is a permanent tissue that forms during wound healing. In some wounds, damaged skin tissue cannot be replaced by new skin or repaired during wound healing. Instead, a fibrous tissue is formed to cover the break in the skin. This fibrous tissue constitutes the scar, which remains permanently. The skin area that is eventually replaced by scar tissue may have scab formation in the initial stages of wound healing. Ultimately, the scab gets replaced by scar tissue.

Causes of Scab Formation

Scab formation is a natural step in the wound healing process. Breaks in the skin that are accompanied by rupture of cutaneous blood vessels typically lead to scab formation as the blood vessels get repaired and the wound heals. Conditions that can lead to formation of scabs include minor injuries like cuts and skin diseases such as psoriasis. On the other hand, wounds that are too large and deep to be bridged by new skin usually do not lead to scab formation.

In such cases, surgical stitching of the wound can bring the broken skin surfaces close enough for scab and scar formation to occur. The following are the most likely causes of scab formation.


Trauma or injury is typically the most common cause of scab formation. Injuries that are prone to scab formation include cuts in the skin caused by knife, burns, falls, assault, contact sports, and insect bites. Even scratching the skin vigorously can lead to bleeding and skin injury. Scab formation occurs when the injury is characterized by a break in the skin and bleeding.

Skin disease

Scab formation can also occur in certain skin diseases that cause breaks in the skin and rupture of cutaneous blood vessels. Examples of such skin diseases include contact dermatitis, atopic dermatitis, psoriasis, cold sores, and chickenpox. In many of these conditions, the skin becomes intensely itchy. Vigorous itching can lead to skin injury and bleeding, paving the way for scab formation.

Other causes

In some rare conditions, minor trauma can cause bleeding and scab formation in multiple regions of the body. In such conditions, skin breaks may occur continuously in various parts of the body in an almost spontaneous manner.

Taking Care of Scabs

Since scab formation occurs during the last stages of wound healing, no medical intervention is required. However, there are a few things to keep in mind in order to prevent aggravating the injury.

  • One should not pick a scab prematurely as it will lead to a delay in the wound healing process and cause more bleeding.
  • The area around the scab tends to get itchy. However, it is advisable not to scratch this area since it can disrupt the scab and cause more bleeding. The resultant open wound may also get infected.
  • The skin area where the scab is present should be protected from further injury.
  • The area of the scab should be cleaned gently in order to prevent disrupting the scab. Antibacterial soaps can be used to clean the area and prevent chances of infection.
  • If a scab gets disrupted, antibacterial cream should be applied to prevent potential infections.

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