Never heard of itch, but ich is a parasite. The only way to rid it from your system, it to remove all fish to a qt
tank (leave inverts and corals, they are not hosts).
Treat the fish with cupramine (copper) or better yet hyposalinity and leave the main fishless for at least 6 weeks. This allow the parasites to go through their lifecycle and die off from lack of hosts.
Any med that claims to be reef safe isn't strong enough to kill the parasites and any med that is, can cause you tank to crash. Thats why we advocate the use of a hospital tank to treat. Duel purpose.