Zyrtec and environmental allergies

My son is in second grade and has been on Zyrtec and singular since he was four years old. He was diagnosed with asthma and peanut and tree nut allergies. He has always been the sweetest kid. However, we noticed in first grade that he was spacing out and not always focused. he became easily frustrated, did not want to do his homework, cried for everything and gave up easily. This year in second grade we are noticing the same thing in addition to talking back, being aggressive with his brother, rolling his eyes and having a nasty disposition. He is negative and complains a lot. His grades have been suffering greatly. He rushes through his school work and does not pay attention or try.
I am so happy for the reading that I am seeing on this site. My son is coming off the singulair and the Zyrtec first thing in the morning.

My son was on a cocktail of Singulair, Zyrtec, Astellin and Nasonex. Like a miracle, his severe allergies cleared up almost immediately. Months later, behavioral changes started to surface. Extreme irritability, major meltdowns over nothing, problems in school and pulling out his facial hair including eyelashes and eyebrows. We stopped the medication in April and he improved. By mid summer, the hair pulling stopped. When his allergies started up again about 10 days ago, I put him back on the Zyrtec, because I was certain the Singulair was causing most of the problems. Within 3-4 days, the emotional outbursts started, panic attacks that never happened before - he said he couldn't breathe. Now the hair pulling is back. Everyone thinks I want to blame medication for his problems, but I am certain that Zyrtec has something to do with these problems in addition to Singulair. We have taken him off Zyrtec 2 days ago. We have a dr. appointment in 2 days and we will discuss all of this with him. In the meantime, his allergies are back and he is miserable. I would rather him be physically sick than mentally at this point.