There’s a VERY good chance it is, in fact, allergies…the question is whether this is environmental or related to food.
So, here’s an easy thing to rule out: what does your dog eat? If a dry kibble, what brand and formulation? Chances are you need to pick up a higher quality food with a novel protein. I would try something with zero corn or other grains and a protein source that *isn’t* chicken or beef. Ideally the food will have meat as the first three ingredients.
While you’re working on a food change, wash your dog’s paws every time she comes inside from the yard. Give them a good rinse with apple cider vinegar, too.
Finally: involve the vet. Depending on the severity of the reaction, your dog may very well need meds to get past this initial itchy spot.
What do you feed? If there’s any grain or chicken in the food, try something else. You want grain free and something with a novel protein. I would also wash his feet every time he comes back inside and if this persists I would head to a veterinary dermatologist.