Dr Fitzgibbon: "The only reliable way is the low allergy diet. For two weeks eat only fresh fruit (but not citrus), fresh vegetables (but not potatoes or sweetcorn), fresh meat, poultry, fish, nuts, olive oil, sea salt (no additives).
I would say that the allergy diets are typically low in protein and often do not provide enough nutrients for an active hunting dog or a growing puppy.
"People think milk is fattening and it's often one of the first things people drop on 'allergy diets' to stop bloating, period pain or other health problems," says Sarah Stanner of the British Nutrition Foundation.