Check the ingredients in his diet and consider trying something different. Try to find one that a good meat protein and few fillers.

Check your house for anything that emits fragrances, such as plug-ins, reed diffuser oils, furniture and carpet cleaners.

Make sure his bedding isn't washed in perfumed detergent.

If the itching/sneezing continues seek out a vet that specilizes in dermatology.

Some pollens move on the breeze, especially grasses. So what you may, or may not plant, might not make a difference.

Several of my dogs were allergic to grass pollen. How do you convince a dog not to sit/lie on the grass

Those same dogs had food allergies, one to beef, the other 2 to grains, but not the same ones.

Veterinary allergists can test for allergies. Food and/or environmental.

And/or a food trial may be worth your time. Only one food at a time for 6 weeks, and that does not mean one packaged product. The popularly suggested guideline of avoiding certain grains, or feeding only raw, may fail.

Because you say it’s the lower part of his limbs that are trouble spots, I would say he’s probably allergic to some of the mites and allergents in the grass he’s walking through. An allergy test will tell you specifically what those are and then the vet pharmacy can mix a custom serum that will help their systems manage better. I had that done for our dog when she was chewing, her feet and lower legs, scooting and burdened with ear infections all the time. To my surprise she was allergic to yeast as well as several mites including grain mites. She gets 2 drops of the serum with each meal and the drops which are a bit pricey last for about 6 months. The yeast allergy also extended to any foods brewer’s yeast in them so I also had to find a kibble that was yeast free. And even though she’s on a grain free food, the Vet suggested we freeze her food for 48 hours before feeding it to her. It took a while for it to all kick in but those changes and the serum have done the trick!