Cairn Terrier

Question
My 5 year old terrier has started scratching and biting himself.  Red skin and loss of hair from this.  Maining from his back end, tail, stomach.

Answer
Sounds like an allergy to something, Suzanne, or it could be mange. The first thing I would do would be to have the vet do a skin scraping to make sure there are no sarcoptic mange mites on him. Then, I'd rule out fleas (the vet can help you determine if it's fleas, too). After that, I'd think back to see if I remembered him scratching around this time last year or not (it could be seasonal allergies). If all of those are a 'no,' then it's probably food related.

I would encourage you to take a few minutes to read the information at http://dogfoods.angelfire.com about dog foods. It sounds like a change is in order for your little guy.