You are the official, and part of the official’s responsibility is to recognize a possible suspicious contagious skin problem for the safety of all who compete on the mat.
It is the coach’s responsibility to look out for the safety of his wrestlers, and the official looks out for all. If the coach cannot present proof to your satisfaction his wrestler is clean of any contagious skin fungus, virus, or staph infection, it is your job to tell the coach and wrestler he/she will not be allowed to compete in tonight’s match.
