You should never use Retin-A over your scabs because it does not assist in the healing process. On the contrary, it can actually delay the healing process. However, it can be used for terminal differentiation of skin cells. This means it can help skin cells from the bottom layer of the epidermis, or the basal layer, mature to the top layer, or the corneal layer. Even so, there is no data that can help support the healing process.
Retin-A will only delay the healing process because it can cause a low level of irritation to the skin. The skin then has to respond to this irritation prior to healing. This is why it is important to keep Retin-A off of your skin while it’s healing the scabs.