Scabs usually fall off a simple scrape wound after a week or two, states WebMD. Deeper or larger cuts, punctures and other more serious wounds take longer to heal and may need medical attention.
Age, obesity, diabetes, alcohol consumption, smoking, medications, infections and poor blood flow prolong the healing process, according to Medline Plus. Picking at the scab lengthens the healing time and may create a scar.
The scab acts as a barrier to infection, allowing white blood cells to repair the underlying blood and skin cells, states Medline Plus. Wounds on or near a joint can crack and leak clear yellow or pink fluid, permitting an infection to develop. To avoid infection, patients should keep the wound clean. The scab decreases in size as the wound heals and eventually falls off.