My son is 13 yrs old and he was given Singular for his allergies....

My son is 13 yrs old and he was given Singular for his allergies. He only takes them every now and than the last time was a week ago. That night he came to me complaining about his stomacher hurting. I told him that it was just something he ate. He also was very angry that night. It seemed like any time his dad or I said anything to him that he would start raising his voice to us. Needless to say that he got into trouble for his behavior. Now that I found out about the side effects of Singular I feel bad that I got onto my son for something that was not his fault and out of his control. This really upsets me to think that there is other kids out there on this medication.