If your dog is licking paws, loosing hair, getting reoccurring ear infections, urinary tract infections, hives or has a stinky smell then they might have allergies. Allergies can be present for all kinds of reasons although food is the most common cause and tracking them down can be daunting and expensive. As you know allergies are often painful, can make you tired, uncomfortable, and sometimes downright irritable. For dogs it can be the same which makes good behavior less likely and training/learning harder.
If I suspect allergies I generally start with a scan from Glacier Peak Holistics which tends to be cheaper than veterinary exams and covers more possible triggers, following up with my veterinarian if I can't get the allergies under control with simple diet changes.
Options when dealing with food allergies.
Here's the scan that I use
Allergies are no fun!