Scab

What is a scab?

A scab is a hard, dried blood clot that can form over a cut or broken skin to stop bleeding and protect the tissues underneath from germs. A scab is a part of wound healing, but not all wounds result in scabs.

Healthcare providers may call scabs “crusts.”

What is the purpose of a scab?

A scab has two jobs:

• To stop wound bleeding.
• To protect the wound.

A scab is essentially a blood clot on the surface of your skin. When your skin experiences damage — like a cut or scratch — and it bleeds, a blood clot forms to stop the bleeding. After some time (a matter of seconds or minutes), the blood clot dries. This is a scab.

A scab also protects an injured area from germs and other irritants that could cause a skin infection or interfere with the healing process. You can think of a scab as a mini shield. It’s the wound’s first form of defense against invaders. It’s also hard like a shield.

Scabs generally remain firmly in place until the skin underneath heals and new skin cells appear. Once your skin has properly healed, your body no longer needs the scab — it eventually falls off.

While scabs are good at protecting damaged skin, they can actually delay wound healing compared to wounds that don’t form scabs. The quickest way to heal these injuries is to clean them, keep them moist with petroleum jelly and cover them with a bandage. This strategy may also lower your chances of developing a scar.

What causes scabs?

Scabs can form when you have a skin wound — typically one that bleeds. A skin wound results from the breakdown of the epidermis (the outer layer of your skin).

Scabs usually develop when a skin wound remains dry. If the environment around the wound stays moist (such as with antibiotic cream or petroleum jelly) and protected, a scab may not form.

Scabs may develop from the following wounds:

• Cuts.
• Scrapes.
• Puncture wounds.
• Burns.
• Pressure sores.
• Surgical incisions (cuts).
• Skin biopsies.

Certain skin conditions can lead to scabs if your skin breaks open. Examples include:

• Acne.
• Blisters.
• Bug bites.
• Chickenpox.
• Cold sores.
• Eczema.
• Folliculitis (infected or inflamed hair follicle).
• Impetigo (a type of skin infection).
• Psoriasis.

What is a scab made of?

A scab is a dried-up blood clot. It’s a combination of:

• Platelets: These are tiny components of your blood that help with clotting. Platelets are your body’s natural bandage to stop bleeding.
• Red blood cells: Red blood cells, also known as erythrocytes, deliver oxygen to the tissues in your body.
• White blood cells: White blood cells, also known as leukocytes, are responsible for protecting your body from infection.
• Fibrin: This is a blood protein that’s sticky and looks like long strings. It forms a fibrous mesh that stops blood flow.
• Plasma: This is the liquid component of blood.

Sometimes, a scab may have tiny fibers in it, like small hairs or clothing fibers. This can happen if they stick to the blood before it dries completely and forms a scab.

What color are scabs?

Scabs are usually dark red or brown. The color can lighten as the wound heals and new skin under the scab develops. But scabs can be other colors for certain reasons:

• White scabs: When a scab turns white, it’s usually due to moisture within the scab. The normal red or brown color of a scab can change when it’s exposed to water from a bath or shower, for example.
• Yellow scab: A scab may have a yellowish color if there’s serous drainage at the healing site. Serous fluid (serous exudate) is a yellow, transparent liquid that aids the healing process. A scab may also appear yellow if the wound is forming an infection.
• Green scab: A green scab typically means the wound is infected. With an infection, yellow or green pus can build up under the scab (and possibly ooze out), changing its color. You’ll likely have other symptoms of an infection, like excessive redness or skin discoloration and pain.

Why do scabs itch?

Scabs may itch as a natural part of the healing process. Your body releases certain cells (like histamine) when you experience an injury. This can cause inflammation and itchiness. Dry skin around the wound and scab may also cause itchiness or make the itchiness more intense.

Try your best to avoid scratching a scab and the area around it. If you break open your skin again, it can slow down the healing process and increase your risk for infection. If you have excessive itchiness, talk to your healthcare provider.

What are the signs that a scab is infected?

Signs that a wound with a scab is infected include:

• The scab is growing in size over time.
• There’s redness or skin discoloration around the scab that’s getting more intense in color or size. (It’s normal to have slightly pink or reddish skin around the injury.)
• The wound is becoming more painful.
• There’s yellow or green pus seeping out of the scab.
• Excessive warmth around the injury.
• Having a fever of 100 degrees Fahrenheit (37.7 degrees Celsius) or higher for more than four hours.

See your healthcare provider if you develop these symptoms. You may need an antibiotic to treat the infection. You may also need medical wound care.

Scabs that won’t heal

Certain factors and conditions can prevent wounds with scabs from healing or slow the process, including:

• Wound size: The larger the wound and scab, the longer it takes to heal.
• Infection: This can make a wound and scab larger and take longer to heal.
• Smoking: Smoking can significantly slow down the wound-healing process. It narrows your blood vessels, which slows the supply of blood, oxygen and nutrients to the healing wound. It also increases your risk of getting an infection.
• Undermanaged diabetes: Undermanaged diabetes can cause poor circulation, which affects wound healing. If you have diabetes-related neuropathy, this can also affect how wounds heal.
• Weakened immune system: People who are immunocompromised are at an increased risk of infection and slower-healing or recurrent wounds.
• Age: In general, the older you get, the slower your body heals.
• Medications: Certain medications, like corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs) and some chemotherapy medications can slow healing.

Call your healthcare provider right away if you have:

• Signs of infection.
• Black edges around the injury. This is a sign of dead tissue (necrosis).
• Bleeding at the injury site that won’t stop after 10 minutes of direct pressure.
• Pain at the injury site that won’t go away, even after taking over-the-counter (OTC) pain relievers.
• A wound that’s come open or the stitches or staples have come out too soon.

How long do scabs take to heal?

In general, it takes at least a week for a wound with a scab to heal and no longer need a scab to protect it. But several factors can affect this, like the size of the wound and if you have underlying conditions that make your body’s healing process slower.

How can I make a scab heal faster?

Wounds typically heal faster when you keep them moist with a wound care cream or petroleum jelly compared to if you leave them dry. Moisture helps new skin cells form and repair the wound.

This may also apply to scabs. Keeping a scab moist with petroleum jelly and protected with a bandage may help the wound heal faster than if you leave the scab dry. Whether the scab is dry or moist, it’s important to make sure it doesn’t peel off prematurely. A bandage can help prevent this.

Keeping the wound and scab clean also helps prevent infection, which slows down the healing process.

Should I peel or remove a scab?

You shouldn’t peel or remove a scab because it can slow down the healing process. When you prematurely remove a scab, you’re also removing some of the newly formed skin tissue growing underneath.

In addition, if you peel a scab, the revealed skin may be red and oozing. This can cause a new scab to form. The more a wound has to form new scabs, the more likely you’ll develop scar tissue.

Lastly, when you remove a scab, you’re taking away your body’s shield against unwanted invaders, like germs. This can make you more vulnerable to an infection.

A note from Cleveland Clinic

Scabs — we’ve all had them. Although they can sometimes look kind of gross or be annoying, they’re an important part of the healing process. Try your best to keep your scab intact and take care of your healing wound. If you develop signs of an infection or your wound isn’t healing, see your healthcare provider. They can recommend treatments to get you back on the healing track.