Jane, I know your pain. Our girls started at about age 7, too. Based on our experiences, I would suggest that you immediately try to remove any artificial colors from his diet. Twizzlers, Skittles, M and M's, Trix, Lucky Charms, etc... etc... All those colors, like Red #40, Yellow #6, etc... can trigger the need to tic (among many other behavioral reactions).
Find as many substitutes as you can that are all natural. Do that for a few weeks, and you might see some dramatic improvement. We did.
Best of luck.
Jeff