I have been really stressed out about the behavior of my 5 year o...

As I read your comments ( and read them to a co-worker) I felt like I had written this. My son is 5 years old and has been on Singulair for roughly 6 months for allergies and we have been experiencing the EXACT things you have. My normally sweet little boy has been having these very same problems and i thank God for answering my morning prayer by guiding me to google for answers this morning.

I posted the message prior to yours, and I, as well, am baffled at the number of complaints about Singulair! Even after reporting the side effects to our doctor, they still weren't convinced it was the medication. My daughter also was fine at school (I contacted her school counselor and teacher). My husband was starting to think that she needed some sort of therapy! Thankfully, within 2-3 days after stopping the Singulair, she started improving and returning back to normal. Hopefully your son improves soon!