While Singulair does work, it comes at a horrible price! We started our 6 year old daughter on it for extreme allergies. Within 5-6 days of starting it, she started becoming angry, moody, aggressive, irritable, throwing horrendous fits and she started crying a lot. She also stopped eating and complained of nausea often. I started to wonder if the Singulair was to blame, so we stopped it. Within a few days, she started improving, and is now almost back to normal. It did help with her allergy symptoms, but I will NEVER give this medication to my children again. Our doctor never once mentioned that side effects like these are possible, but apparently they are.