The most common causes of an itchy scab can be traced to the natural healing process as new skin forms over the injured site and gradually separates from the scab. An itchy scab can also result from certain skin conditions, such as eczema and psoriasis, or from a herpes viral infection. Some people who are prone to contact dermatitis from skin allergies may experience rashes that later turn into patches of itchy scabs. Dermatologists frequently advise that time is a key factor to successfully heal a scab resulting from any of these conditions, so they also usually caution their patients to resist the urge to scratch or pick a scab regardless of how badly it may itch.
A scab forms over a variety of surface skin injuries such as cuts, deep scrapes, minor to moderate burns, or shallow abrasions. Some people report that milder skin scrapes can itch worse than more serious ones during the healing process. Soon after the skin injury happens, the body's natural immune defenses cause bacteria-fighting white blood cells to travel to the wound site and begin forming the protective scab. Many cuts, burns, or scrapes involve microscopic nerve damage just below the skin's surface, and a scab allows these tiny fibers to begin rejoining with a lower risk of bacterial invasion. Itching at the wound site is a common side effect as these severed nerves exchange confused signals with certain receptors in the brain.
Newer scabs are frequently raw in appearance due to the presence of clotted blood and lymphatic fluid that actively fight infections. Caring for a scab often involves keeping the wound clean and covered with a bandage or piece of gauze dressing. Scabs resulting from allergic rashes or certain skin conditions often need additional treatment, such as a prescription topical ointment designed to counter the inflammation. These kinds of medicines also usually have an added benefit of relieving a persistently itchy scab.
An itchy scab can sometimes be noticeably bothersome as the scab dries out several days after the initial injury. Healthy scab colors can range from yellow-brown to nearly black, and this appearance is normally not a cause for concern. One of these scabs on a joint such as a knee or elbow often heal better with the regular application of antibiotic ointment that prevents them from cracking and reopening the wound. An itchy scab with a red ring around its edge usually indicates an infection that may require a physician's attention.