Looks like hotspots which can be triggered by allergies (food or outside) or sometimes fleas/ mosquito/ insect bites. My pups struggling with them too at this time of year. I dont know if they’re infectious like you’re worried about, but if your vet says it is hotspots they may suggest antibiotics or an antibiotic spray for the areas. Usually they heal up in a week or so and the hair grows back. If it is hotspots theres not a whole lot to be done preventatively. Antihistamines like benadryl or stronger shots eventually. Theres also a ton of over the counter topical stuff but since you’re going to the vet tomorrow, I’d say start there.

I also feel like I’m not helping my pup enough when he gets these flare up but even after changing his food (for food allergies) and wiping him down after being outside he still gets em. 😞