This three year old neutered female West Highland White terrier was presented with an eighteen month history of severe, non-seasonal pruritus and self trauma. She had been diagnosed with house dust mite allergies on the basis of a blood test a year before the photograph on the left was taken. She had been treated with a course of desensitising injections but this had not resulted in any improvement. To rule out the involvement of a food allergy, she was started on a diet trial consisting of pork and potato. After two months her itching had stopped and her hair was regrowing (below right). To make sure that it was the diet that had resulted in the improvement, we reintroduced her original food and within 48 hours she was starting to show signs of itch again.