Food allergy / intolerance
An adverse reaction to a food component, most often a protein. Causes skin or gut signs. Diagnosed by 8–12 week elimination diet.
Food allergies and intolerances in pets cause chronic itching (often face, ears, paws, anal area), recurrent ear infections, chronic soft stools or diarrhoea, or chronic vomiting. The most common trigger is a protein the pet has been eating for a long time — chicken, beef, dairy, lamb, fish, egg, or sometimes a wheat or corn ingredient.
True diagnosis is by **elimination diet trial**: 8–12 weeks of feeding ONLY a hydrolysed-protein diet or a strict novel-protein diet (one the pet has never had before), with absolutely no treats, flavoured medications, or table scraps from other family members. The strictness is the whole game; a single contaminated week resets the clock.
Blood tests and saliva tests sold as "food allergy panels" have poor evidence behind them and are not a substitute for an elimination trial.
After 8–12 weeks of clean diet trial with improvement, you challenge with one suspected ingredient at a time to identify the culprit, then choose a long-term commercial diet that avoids it.
The hardest part of an elimination diet trial is the family — children sharing toast, grandparents slipping treats, the dog finding the cat's food. Without 100% compliance, the trial doesn't give a clean answer.