Here's a little about what we experienced with food sensitivities.
Before we changed diet, my son was experiencing a number of tics, which, in retrospect, I now attribute to a probable genetic predisposition that was exacerbated by poor gut health brought on by poor diet (even though we though we had a pretty healthy diet!). Since his tic condition problably caught our attention only after it was exacerbated by years of deteriorating gut health that went unnoticed, improvement has been associated, in my non-expert mind, with improved gut health, which has taken time. So some tic improvements may take time.
Nonetheless, once we decided to take long term steps (diet modification and supplements) and really focus on food triggers, we found ourselves picking up on foods that were offenders pretty easily. That is, his normal or "baseline" ticcing got noticeably worse fairly shortly after consuming a trigger food. This would tell us what to eliminate from his diet, and would also quite often land him in a bath of epsom salt, which has always been pretty effective at bringing tics back down to his baseline level.
Slowly but sureley, his tics have become less and less, due, again in my non-expert opinion, to gut health which has improved slowly but surely, and a few key supplements. Now, when we allow him (ocassionally) to have foods that were once triggers, he tolerates them with no noticeable tic increase. But we are still vigilant and still restrict what he eats.
One anecdote I have concerns one of the last truly noticeable differences in his level of ticcing. After a good year or so of the new diet, we were all at a comfortable spot with the improvements we had noticed. But we were still working. One day, I noticed my son's tics increase after eating an orange. Should have picked up on that before, I guess. It just so happened that I was giving him his multivitamin (one of the most notieceably beneficial supplements we use) in orange juice every morning. Stopped that the very next day, and within a week we saw a very noticeable decrease in tics.
Hope this info helps answer your question.
- Chris