Katherine:
Yes, there are several variants of what is called
vasculitisNecrotizing vasculitis, or inflammation of the blood vessels.
Most rashes "look" contagious, especially red ones, even more especially in food-service contexts. I am confident that your co-worker's physician wouldn't let him back to work with a contagious condition. As for the customers, if your superiors aren't worried about putting them off, I think you be relaxed about it.
Best.
Dr. Rockoff