What Are Scabs?

Scabs are patches of dry, tough skin that form over a wound during the process of healing. It is important to make sure that scabs stay protected to ensure proper healing of your skin and to prevent the risk of infection and scarring.

healing scab on leg

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How Do Scabs Form?

Scabs form after injury to the skin and promote wound healing, which can take months or even years to complete.

The four stages of wound healing are:

  • Hemostasis and degeneration
  • Inflammation
  • Proliferation and migration
  • Remodeling and maturation

Hemostasis and Degeneration

Hemostasis, or the stopping of blood flow, occurs immediately after the skin is injured to prevent excess blood loss. Coagulation, or blood clotting, begins as platelets from the blood clump together to form a loose clot, which turns into a scab as it dries and hardens.

These platelets release chemical messengers that send signals to bring inflammatory cells to the site of the injury to initiate the healing process.

Degeneration occurs through the formation of a hematoma, or pooling of blood under the skin, as well as deterioration of dead skin cells and the initiation of an inflammatory response.

Inflammation

In the inflammatory phase of wound healing, fluid is brought to the area of injury to dilute harmful substances and provide support for cells to fight infection.

Once the blood clot is formed, an increase in blood flow to the area stimulates cells to travel to the area of injury to destroy bacteria and release substances that support the formation of new skin cells to repair the injury.

Approximately five days after injury to the skin occurs, fibroblasts and skin cells migrate into the wound to form granulation tissue, specific connective tissue that forms in the area of a wound to promote healing.

Dead cells are broken down and removed, and tissue healing begins in this stage.

Proliferation and Migration

Two days after injury to the skin, cells begin to form blood vessels near the edges of the wound. These blood vessels begin to proliferate, or increase in number, to promote a network for delivering oxygen and nutrients to support the healing skin tissue. The process of forming new blood vessels is called angiogenesis.

As the number of inflammatory cells decreases at the area of injury, new cells migrate to the wound to repair the skin. These cells form collagen and elastin, structural proteins that cross together to form a scar.

Remodeling and Maturation

In the final stage of wound healing, the scar tissue that forms is remodeled to a smoother appearance that is reduced in thickness and redness as the concentration of blood vessels in the area decreases. The remodeling phase of wound healing can take years to fully lighten a scar to more closely resemble regular skin tissue.

Even under ideal conditions, the repaired tissue that forms when an injury to the skin heals never regains its full strength and stability. It can take up to 12 to 18 months for a scar to fully mature, and at this point, it is approximately 20% to 30% weaker than normal skin tissue.

Why Do Scabs Itch?

Many of the cells involved in the stages of wound healing release cytokines, inflammatory proteins that, in addition to increasing the inflammatory response, can cause itching. Changes in the level of pH and nerve signaling stimulated by tissue tension as an open wound begins to close and heal may lead to itching as well.

Specialized sensory nerve cells in the skin—called pruriceptive neurons—respond to these changes and send signals to the brain, where the sensation of itch is recognized.

Wound dryness that develops as a scab forms and hardens can also cause itching, potentially by blocking sweat ducts and activating enzymes that increase itching. As a wound heals, the itching sensation decreases as nerve stimulation and blood flow to the area slow down.

Complications

Complications can occur that cause wounds to become chronic, taking a very long time to heal or not heal at all. Three main factors that impair the ability of wounds to heal include:

  • Poor blood supply and lack of oxygen
  • Excessive proteolytic activity
  • Infection

Blood Supply and Oxygen

All tissues of the body require a good blood supply to get oxygen. When blood flow is disrupted through damage to blood vessels, tissues become deprived of oxygen, which leads to cell damage, and in severe cases, cell death.

Cells that are involved in the wound healing process have high demands for oxygen. Prolonged lack of oxygen, called hypoxia, can significantly delay wound healing.

Factors that contribute to poor circulation and reduced blood flow and supply of oxygen include:

  • Older age
  • Diabetes
  • Arterial or venous diseases that damage blood vessels
  • Necrotic wounds that result from significantly damaged tissue from injury, burns, disease, or infection

Proteolytic Activity 

Proteases, also called proteolytic enzymes, are found in the fluid that leaks from wounds. While they are essential for wound healing by breaking down proteins and restructuring the skin, they can become harmful to wound healing when there is excess activity as a result of chronic inflammation.

Proteolytic enzymes are released by cells involved in tissue repair that are stimulated by the inflammatory response. During the normal phases of wound healing, proteases reach peak levels three days after injury and decrease after day five.

With non-healing wounds, levels of proteases peak significantly higher at day three and persist for much longer, causing a destructive environment that does not promote wound healing. A class of medication called protease inhibitors can be helpful for promoting healing of chronic wounds to lower the activity of these destructive enzymes.

Infection

When the skin becomes damaged, bacteria naturally found on the skin surface can enter the wound and cause infection. Bacteria can also stick together in a wound, forming a protective biofilm that decreases the ability of white blood cells to fight off the infection and reduces the effectiveness of antibiotic medication.

When to Call a Doctor

You should contact your doctor if you think your wound is infected. In addition to a slowly healing or non-healing wound, signs of an infection include:

  • Redness 
  • Swelling
  • Warmth 
  • Pain or tenderness 
  • Oozing pus or liquid, called wound exudate

How to Help Scabs Heal

You should avoid scratching at a scab so that you do not cause further breaks in the skin, which can disrupt the healing process and increase the risk of infection and scarring.

To help relieve itching, use a moisturizer to help prevent loss of water from the skin and decrease dryness that can cause itching. Cooling ointments that contain menthol can also help decrease stimulation of the sensory nerves on the skin to help alleviate itching.

To prevent infections, wounds should stay clean and moist. Wounds need some moisture to promote migration of new skin cells over the wound bed, so the wound should be kept moist but not too moist.

Antibiotic skin ointment can be applied topically to an open wound to prevent infection. Covering the wound with a sterile bandage can also help decrease the risk of infection by creating a barrier between your skin and the outside environment.

Summary

Scabs form to help your skin heal after injury. However, they do come with discomfort like itching during your recovery process. It’s usually nothing to worry about, but if you think your wound is infected, call your doctor to receive further medical care.

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