My son now 12 has been on Singulair for 5 years, ever since we moved to Florida and figured out he is allergic to half of the crap that grows here. The only problem my son seems to have is that twice he has gotten thrush from it, from not rinsing his mouth out and then eating something right away. While I am now watching him for the other side effects listed here. He is still the same charming funny bright child he has always been. Still on the Honor Roll and still in gifted classes. Singulair isn't for everyone, but it does work for some!