http://www.medications.com/effect/view/28649 No side effects here - my 5 year old has been on Singulair since he was 2 1/2 and has showed no strange symptoms outside of those of a normal 5 year old boy. He has asthma and severe allergies - including a nut/peanut allergy. He also takes Zyrtec in the Fri, 28 Mar 2008 20:50:11 -0400 http://www.medications.com/effect/view/28649?item=6093 Yes, the boards on other drugs do list extreme reactions, but if you look around, you won't find many with as many postings as this Singulair board has. I was shocked by how many postings there are here. And yes, this board had over 1000 posts even befor http://www.medications.com/effect/view/28649?item=6093 Sun, 30 Mar 2008 18:15:38 -0400 http://www.medications.com/effect/view/28649?item=6235 i have to agree with this posting. My son is 4 and has been on singulair for 1.5 yrs and he is an average child. He is patient, kind to friends and family, he does get short tempered every now and then but I think this is just typical behavior for a boy http://www.medications.com/effect/view/28649?item=6235