I'm so glad I found this web site.
My 5 yo son's pediatrician put him on Singulair three weeks ago to help with mild asthma/seasonal allergies. Two days after starting the drug, he began to hit himself, and say he was stupid and a loser whenever he made a mistake. He is NOT the child who would naturally do these things, he is always the first one to tell you how great and smart he is. He has also had uncontrollable screaming rages since starting the drug. one lasted 45 minutes. He stood at the top of the stairs and howled and screamed last night until he was sweaty and red, and said "help me mom, I can't stop!". It was frightening. I went on the web afterwards to check for side effects and found this site, which mentioned other side effects he has had that I hadn't attributed to the drug:
He has been getting hives after playing outside. I had attributed it to allergies, although it has never happened before. He has developed sores in and around his mouth, and has pains in his legs that I thought were growing pains. He is officially off of the medication, and I called his pharmacist and doctor today to let them know why.