How can a dog suddenly get mange?

Over the past two weeks my german shepherd has started scratching a lot. His skin has gotten really flaky and he has a terrible odor. None of my other dogs has shown any of these symptoms. I did change his food around the same time and I'm just wondering if he may have a food allergy, since this just kind of came out of nowhere and only affects him.

mange is caused by a mite - either demodectic or sarcoptic - and needs to be diagnosed by a vet.If your dog has dry skin, dandruff and is itchy is may be something lacking in his diet - like fatty acids - or a reaction to something in his environment.Try adding fish body oil to his diet (soy free) - I use capsules meant of humans and use them a few times a week but some people add these every day.

To be sure that it isn't mange take your dog in to see a vet. If you take the dog off of the new food and go back to the old food and the symptoms cease you know it's an allergy. Then you just have to figure out which ingredient(s) it is that he is allergic to.