[Help] What can i give my dog for his skin and to help is hair grow back?

The vet at the shelter says the hair loss is from a flea allergy. I'm taking him to a vet appointment on Saturday, but was wondering if anyone has any recommendations for topical treatments or supplements I could give him in the meantime?Here's what his back looks like now via /r/dogs http://ift.tt/2qLdAJ9