My Dog Is Losing Her Hair…does Anyone Know If This Is A Symptom Of Allergy To Fleas? Or Possibly Nerves?

Not that I have seen any fleas, but I’m very concerned for her. She is a lab mix and I think she has some pit in her. She has been staying with my mom because I’ve been in the process of moving and my mom describes her as looking like she has mange. Can a dog lose her hair…literally chew it off because of nerves? I’m about to get her back after months so I will be taking her to the vet soon, but I’d like to do anything I can for her at home to make her comfortable first.