Can i take claritin and benadryl (diphenhydramine) together and drink it down with an alka-seltzer?

Maybe: Depending on what you are treating, i would space them out, take Claritin in the morning and Benadryl (diphenhydramine) at night. Benadryl (diphenhydramine) is sedating though, so be careful driving or operating machines. Not sure what you are treating though. I can see that with urticaria but for nasal allergies, i would use a nasal spray instead of a second antihistamine. Alka seltzer will only help pain because it has aspirin.