It is under the chin, not external at this time, just swelling. Last year though there was some oozing on his fur on the outside of his chin. I think it had progressed further at that time... We treated him with amoxicillin 250 tid and topical cefa (which seemed useless to stay on the affected area. I have 500 mg caps of cephalexin and would like to use it instead of a vet visit to see if it works... if not i'll try the vet in a few days... i've worked with rescue groups, am a retired nurse, live in the desert, am frugal with my 5 critters, but try to get an informed opinion b4 i treat my pets. the vet says that this mimics a type of cancer, that if the rx didn't work, then it could be ca. I will surely evaluate him closely to see if rx works. can i just use the Cephalexin instead of obtaining Amoxicillin?