My son takes singulair prescribed by Pediatrician and is on flovent inhaler 2 puffs a day. Seems to work for him and side effects are minimal.

My son has bad seasonal allergies too and his behavior changes with different medications. Dr. recommended trying 1/2 dose at bedtime of Zyrtec. It has helped allergies and he is sleeping better without coughing all night. Not sure on behavior yet since I have only given it to him for 3 days.

Nasacort just went over the counter. Works really for me and one of my sons

Ok, another tip: NASAL ALLERGY SPRAYS
Flonase, Nasacort, etc. Flonase is generic, cheap, and very effective. There is also a sudafed nasal spray. It stays in the nose and won't affect moods. :)

Benedryl usually has few side effects, too. Don't use antihistamines with any pseudoephedrine in it (sudafed). Any of the ones with a "D" in the name like Allegra-D and Zyrtec-D, Claritin-D, have the decongestant, too. That WILL usually cause major behavior side effects. My son can tolerate it mostly, but my daughter can't tolerate the stuff at all! Major, major problems...