my friend had her boy on it from age 3 till age 9. Finally they made the connection you are making. It had gotten really bad - her son got paranoid and developed phobias about being in a room by himself and being in elevators, flying, etc.
They took him off the singular and within a few weeks he was not having any of those phobias anymore, and sleeping better and not having meltdowns as much at all. The boy said to his mom "I'm so glad I don't get that jittery feeling anymore. I never want to go back on that Singular. It made my skin jump."
SO, that is all the evidence I needed - my daughter went on Claritin this spring when she was diagnosed with seasonal allergies! No issues at all.