We had great success with the Feingold program, and continue to follow a very relaxed form of it. My oldest daughter had fairly severe tics at age 6-7. We started the FG program, and within 2-3 weeks, we saw a dramatic reduction in the tics. For some it takes longer, and for some the symptoms get even worse before they get better. At first we were very strict, including shampoos, toothpastes, etc, but eventually settled on eating all-natural in the house, and not worrying about occasional infractions. It's much easier now than at the beginning. We also discovered the Corn Syrup had a big impact on my youngest DD's temperament. It caused her to be very irritable and lose focus. That was the hardest thing to eliminate, as it is used in so many foods. As they have gotten older (13 and 16), they are able to tolerate more infractions. If they cheat too much, they tic mildly, but we know that, after a few days of clean eating again, the tics will subside.
I highly recommend that people sign up for the program, at least for a few years, read the literature, buy the "approved" products, etc. It's a great education and can change your whole perspective with regard to what you put into your bodies!! You are what you eat!!
Jeff