Our 5 year old son is clearing his throat almost constantly.
He was diagnosed with a 'tic' about a year ago when he shook his head for about a week. Then it was over. There is NO tic history in our family.

He started clearing his throat in Oct 08 but it would come and go. We took him to an allergist and the allergy test showed NO allergies and no signs of asthma. Doctor said it was most likely post nasal drip and prescribed Nasonex. That helped --- he stopped doing it (or did it VERY little) for about a month. Now it's back and it's just about constant for the last few days. I'm about to lose my mind! It gets MUCH worse if he has milk or a milkshake so mucus DOES seem to be an issue. Also, if I tell him to stop he will stop for a minute or so and then starts back up. He says he's doing it on purpose sometimes but I don't know if he really is or not. Zyrtec, Mucinex and Claritin seem to do nothing either.

Habit??? If so, how do I break this or even determine it?
HELP!!???