There are a variety of possible reasons for a scab turning white during healing. The most common cause is that of trapped moisture. During healing, the wound has a variety of layers of new skin, that can easily allow water in. People who come into contact with water often or have a high water content in their bodies will easily develop white scabs. Other reasons may include the application of too much ointment or the fact that the wound has become infected. An infection usually occurs when bacteria come into contact with the wound, and the immune system responds by trying to remove the infection. This is usually couple with red, itchy and warm surrounding skin, and antibiotics may be required to prevent a blood infection.