You could ask your vet for a referral or call the nearest School of Veterinary Medicine. A dermatologist is the only way to get an accurate diagnosis.
They do specific tests to identify, plus they have examined thousands of dogs and can often tell a lot just by examining the dog.
I get it, you don’t want to spend the money. But, in my experience you are likely to spend a lot more going back and forth to the regular vet for band aid treatments, various diets, bogus remedies, air purifiers, dehumidifiers, meat grinders for raw diet.
Been there, done that.
Good luck with whatever you decide.
This is not veterinary advice; consult your veterinarian.
