Original sentence: Also considered "doping" by many is the use of substances that mask other forms of doping.Doping is often considered a form of unfair competition; also, many forms of doping can be hazardous to the sporters' health, with symptoms sometimes not occurring until after the sporting career.In sports the word doping means the use of performance-enhancing drugs, particularly those that are forbidden by the organizations that organize competitions in a certain sport.Some doping substances, however are permitted in low doses (alcohol and caffeine)
Edited sentence: Also considered doping by many is the use of substances that mask other forms of doping.Common doping substances are alcohol and caffeine (though permitted in low doses).In sports the word doping means the use of substances that may increase one's possibilities and that are forbidden by the organizations that organize competitions in a certain sport.While doping is not only a form of unfair competition, many forms of doping can be hazardous to the sporters' health, with symptoms sometimes not occurring until after the sporting career