My almost 7 yr old has been on Singulair since he was 4. He was first diagnosed w/ allergies at 3 1/2 after having 3 sets of tubes, several episodes of pneumonia & bronchiospams. He was put on Pannaz (aka Blues Clues medicine since it's a bright blue color) first and has been on it the whole time just increasing the dose as he's grown. We added the Singulair when he got to the point of playing, coughing, gagging & puking. These 2 meds combined have done wonders for him! We've tried using 2 other meds in replacement of the Pannaz and he started the whole coughing, runny nose bit after 3 weeks.
My 4 1/2 yr old was put on Singulair last fall, Extendryl & QVar (for asthma) in March. He hasn't had the ear infections that my other son had, but he had the virus that turned bacterial and then microplasmic all in 1 1/2 weeks, the pneumonia, the bronchiospasms ~ we haven't used neb treatments since March.
For us, these combinations work wonders!
And about the cavities post I read, my kids just went to the dentist on Tuesday for their yearly check up and all are cavity free. They don't floss either. So I can't say that I've noticed a correlation between using Singulair and cavities.