My son is 11 and started to tic at age 6. We soon realized it was being caused by artificial coloring. As the years have gone by we now know that his tics are caused by artificial colorings, flavorings, and other chemical exposures. If we keep him on a very whole foods diet for one-two weeks, his tics almost completely disappear. Exposure to a tic-triggering substance can cause anything from slight head-jerking to more severe vocal and physical tics.
This problem seems to be getting worse, but I attribute that to the fact that he is getting bigger and requires more food. We ride a roller coaster of sometimes no tics to sometimes pretty bad tics.
I have been curious as to whether other people suffering from TS have had a similar experience concerning substances that they ingest?