What does "reactive epithelial cell changes" mean?

Reaction to injury: Many body structures have an inner lining , somewhat like a "skin" on their service. This is true of the airway or the Gut. This "skin" is made up of a lining cell called epithelium. When these body parts are exposed to irritation or injury there can be changes in the lining cells that reflect evidence of this injury or irritation that are not very specific for any one disease, called reactive.