My 13 year old son has been on sigulair now for several years. I only give it to him during the school year. I have come to realize taht every fall when I restart it he complains of severe stomach aches. As well we have noticed a him morphing into a defiant, easily angered young man. Totally out of character for him. I have now taken him off and will hopefully be able to contro; his asthma with inhalers. No more singulair for us