Allergy medicine?

Hey ladies. My 21 month old dude is going THROUGH it today with allergies. What can I give him? We have the itchy nose, watery eyes, runny nose, sneezing. It’s bad. No fever. We tried are natural herbal antihistamine drops. I read no benedryl and that Claritin or Zyrtec is better. Pretty sure ped said I could do Zyrtec just low dose. But idk how to dose it? Does anyone like one over the other for their kiddo? I saw Dr Talbots has a Homeopathic one. Anyone have success with that?