
One of mine normally gets itchy this time of year (started as a puppy) & the Vets have also said it's the pollen ~ hayfever. Anyway, she was started on normal, over the counter, (from Boots), antihistamine (non-drowsy type). It normally takes a few days to kick in & she also got a regular hose down, especially if she'd run through long'ish grass.
I have to say that she's now 2+ & so far this year, so good in that she's not been scratchy so she has now possibly,
hopefully, grown out of it