When Peanut was having really bad allergies my Vet told me to get the Walgreens brand. It’s called Wal-Finate Allergy Relief:
Walgreens*Wal-Finate Allergy Relief Tablets | Walgreens
I gave Peanut ½ a pill. It really worked well for him. We use K9 Advantix. I've been using Advantix since he was young enough to have it one. I never seen a flea on him or tick.