A scab is simply coagulated blood, a way in which the body protects itself from foreign bodies. An open wound provides convenient access to the body for bacteria, parasites, and dirt, and therefore the body has evolved a method of covering wounds to keep them safe. When you hurt yourself, after bleeding for a while, blood thickens and hardens to form a scab, which functions as a protective covering over the wound. It is therefore important not to peel or pluck at your scabs as, apart from being painful, this will reopen the wound and invite infection. When a wound has healed enough, the scab will fall off on its own. Sometimes, when a wound seems to be excessively inflamed or is very deep, a scab may need to be removed, but this should only be done by a doctor; in any case, such a wound would need regular medical attention.
At the same time though, it is not always advisable to leave a wound to heal entirely on its own. Although antibiotic ointments are not usually needed and are best avoided unless prescribed by a doctor, other measures may be needed to speed up the healing process and minimize scarring. It is advisable to apply some ointment (easily available over the counter) over the scab to keep it moist, contrary to traditional advice which says that wounds should be kept dry. A couple of times a day, you should clean the scab gently, removing dirt and old ointment, and then reapply the ointment.
answered by M W