A friend of mine had a rott that was allergic to certain pollen, it passed when that particular strain went out of season, so lasted 4-6 weeks every year.
I advised thornit between the pads which helped as long as u can stop ur dog from chewing feet.
Another thing is dog boots while the pollen is aggrivating, or ask vet for 4 empty drip bags to make a set (cheaper way) they may even make em for u
If u can during the bad periods walk by the sea?? or have a cool foot bath ready from when she returns from a walk, containing a weak salt solution.
Is it all 4 feet affected or just 2 as if its just the hinds then it may not be an allergy it may be ear mites but am sure ur vet would have checked.