A cut on the skin leads to an open wound that is vulnerable to infections and irritation. As soon as your body detects such an injury, it begins to process of healing that will eventually see the wound close. As you go through the stages of wound healing, a scab will form over the cut to help it heal. The crust can sometimes present as an itchy scab that makes you feel you want to scratch and pick at it all the time.
The itching, however, does not start immediately. As soon as the cut occurs, your body releases platelets to clot the area. “The platelets then rush to the site of damage and form a plug, or clot, to repair the damage.” – University of Rochester Medical Center.
The clot acts as a natural protective bandage that stops more bodily fluids and blood from flowing out. A blood clot is made up of other cells as well, including fibrin, an insoluble protein formed during the clotting of the blood. This forms a fibrous mesh that helps cover the wound.
Soon, the blood clot over your wound starts to harden to form a scab. A scab is a dry protective crust that usually forms over a wound to help it heal faster. It prevents further bleeding and entry of bacteria and other germs into the body via the cut or damaged skin.
Scabs can form anywhere on the skin. The most common ones occur on the legs after shaving and scratching, on the scalp due to psoriasis and dermatitis, and the face due to popped pimples and acne spots. As the wound heals, the scabs can become itchy and irritating, especially if they are dry.
The reason why people pick scabs is that they can be very itchy and feel irritated. All wounds tend to itch during the healing process.
According to the Wound Care Society, “The itchiness comes from the reaction of sensitive nerve cells beneath the skin which react to released chemicals and stretching skin and wound tissues. It is newly researched that our skin is equipped with some nerves which are sensitive to itchiness.” 
The skin contains certain specialized nerve fibers that help it detect when the dermis is irritated. These fibers then send signals to your spinal cord to communicate to your brain that there is an itch. Different things can trigger the nerves in your skin, including an insect or bug crawling on you. For the case of a scab, it is the mechanical stress that is caused by proliferating cells around the wound.
As the cells around the margins of the cut grow and move inwards towards the base, mechanical pressure is exerted, causing the area to itch and irritate. This is just one of the main reasons for itchy scabs on the skin.
Another possible reason for itching wounds is the activation of nerve fibers in the skin by chemicals secreted in the body to help speed up the healing of your wound. The body releases a chemical called histamine.
According to WebMD, histamine boosts the flow of blood in the affected area of the body and results in inflammation. The inflammation process triggers other chemicals in the immune system to fight off bacteria and other microbes to help the healing and repair work.
Wounds and cuts go through 4 stages. From an open sore to a healed skin with no scar, you will likely experience different symptoms, including swelling, inflammation, pain, and aches, and finally, itching that will culminate in a healed injury.
As already learned, the tissue regrowth stage produces mechanical stress on your dermis. This, therefore, becomes the itchiest stage of your scab formation.
Crusts form from various components discussed above. However, there are times when you will see different colors. Most scabs on the face are likely to be yellow, especially if you pick them. However, on bigger wounds, a yellow or light green crust on a wound could be a sign of infection. This is usually accompanied by pus drainage. If you see such a sign, consult your doctor for treatment.
White or grey pus oozing from the wound is also a sign of infection. The white blood cells are active on the site are likely to produce white pus cells.
The red-colored scabs are likely caused by inflammation. This is a sign that your wound is irritated and is likely bleeding slowly. There’s something irritating the area. If you are fond of picking the scabs, you are likely to experience this symptom.
Picking your scabs usually slows down the healing process. Studies have shown that picking and eating scabs on the skin, face, legs, etc. is a sign of an obsessive-compulsive disorder. (Jeanne M. Fama, 2010)
Below the scab, there is a new layer of skin cells that are growing as the wound heals. As soon as the healing process is complete, the will be no more scabbing, and the crust that was formed over the cut is no longer needed. It falls off.
If you pick premature scabs, scar tissue will be left behind even though it wouldn’t normally exist, especially if the cut was shallow. It gets even worse because the regeneration process will start all over again, which means that your popped acne scars, cuts, nipple abscesses, etc. will start to heal again.
Scratching your wound will not help it heal faster. Touching the area can cause an infection that will end up as an abscess. You also increase the risk of scarring if you continually pick and scratch the skin. Here are tips to reduce the itching:
In general, you can reduce itching by keeping the area moist. A dry scab is easily irritated and will easily result in severe itching. If the scab is on your breast due to a nipple piercing infection, avoid wearing tight bras or clothing. Wear loose, breathable clothes to allow the wound time to heal.