Why is it that when a wound is healing it itches?

Wound healing is a very long and complex process which progresses in stages.

Three stages of wound healing can be classified as: I. Inflamation; II. Proliferation; and III. Remodeling.

These stages are fairly well understood and can be further broken down into specific cellular mechanisms that promote wound healing during each stage. The process can ultimately last for months or even years, depending on exactly where it is on the body, what type of tissue it is, and the kind of use that the tissue receives in terms of daily stretching and exposure to the environment. But in general, since sensation in and around the affected area comes from nerve endings (there are no nerve endings inside scar tissue ... but there are all around scars), itching comes from stimulation of those endings. In early healing, such stimulation can come from the processes of healing itself. But later, the mechanicasl stretching of scar tissue next to normal tissues can stimulate nerve endings and cause an itching sensation. This is assuming there is no inflammation around the healed tissue.

Itching can also be an indicator of infection. If the edges of the wound are pink/red, warm/hot to the touch and actually a little painful when being touched, or there is yucky drainage coming from the wound, then it could be infection.

http://www.utahmountainbiking.com/firstaid/pics/infect7.jpg