Do a search on here and you will see tons of threads and links to articles on this topic. It is important to understand how this parasite operates, because part of its life cycle is where those white spots drop off. Most people think the fish is "cured" at that point, which is not the case at all.
You basically have two options if you want to CURE Ich. Hyposalinity or copper treatment in a QT tank. Pair that with leaving your tank fallow for about a month and you end up with Ich-free fish going back into an Ich- free environment. QT future fish and it should never show up again. Adding garlic to food helps build up their immune system, but is not a cure.
Anything other than doing that leaves live Ich in your tank (and possibly still on your fish) and it will very likely come back worse in the future.