My daughter was put on the lowest dosage of singulair that is available at 9 months old. I could not figure out why she wouldn't stop moving, she actually looked like she was on speed. She crawled around non-stop, I could not get her to take a nap, she would not eat, because her stomach kept churning like it was upset. I got really concerned after 2 days of this and I looked up the possible side effects of singular. What I found weren't side effects, but signs of an overdose...you might want to check the dosage if you are having any of these reactions to this medicine.