Why does a scab turn dark?

A scab turns dark primarily due to the oxidation of hemoglobin in the blood that has pooled in the dried wound. As the blood dries and exposure to air occurs, the red blood cells break down, leading to the formation of dark pigments. Additionally, the presence of proteins and other substances in the dried blood can contribute to the scab's dark appearance. This process is a natural part of healing as the body works to protect the wound underneath.