My lab keeps scratching his ears nonstop - food allergy or spring pollen?

My 3-year-old yellow lab Tucker has been scratching at his ears nonstop for the past two weeks. Like constantly shaking his head and digging at both ears with his back paws. i checked and there's no obvious discharge or smell, so i dont think it's an infection. but it started right after we switched him to a new kibble brand, which also happens to line up with peak pollen season here.

So now i'm stuck trying to figure out if it's the food or just environmental allergies. Has anyone gone through this and actually figured out which one it was? i dont want to drag him to the vet for a full allergy panel if this is something i can troubleshoot on my own first. Any advice would really help.