WOW!!! I am in awe reading these posts! I recently began taking Singulair. It has been about a month now. I have experienced sore throats, irritability and also weight gain. I noticed that my appetite hasn't changed much, but I gained I know at least 5 lbs. I decided to check out the side effects of Singulair and I'm glad I did. I won't be taking it anymore. I am also taking Zyrtec. I have been taking that for about 6 months now and I didn't notice any problems with taking this med.
My 8 year old son takes it as well and I can say that he has not had any problems that I am aware of. I guess each person is different.