A friend told me today that she took her son out of Singulair because of the terrible nightmares he was having whilentaking it. I have not slept well in the last year and a half that my 2 1/2 year old son has been in Singulair but never though it was due to the drug since he was doing so well with the post RSV related asthma. I am taking him off today, I hope he can sleep better and his bad temper and aggressive responses cease. He was never like that before. I can believe that so many people have gone through the same situation with their kids and I never heard about it until today