Glossary

Limited-ingredient diet

A food built around few ingredients, often a single protein, used in a vet-guided trial to find out whether a cat has a food allergy.

Also called: LID, elimination diet, novel protein diet, hydrolysed diet, food trial

A limited-ingredient diet contains a short list of ingredients, typically one animal protein and one carbohydrate, to reduce the chance that a cat meets a trigger. Some are sold over the counter. Veterinary versions use a protein the cat has not eaten before or proteins broken into tiny pieces, called hydrolysed, so the immune system does not recognise them.

Vets use these foods for an elimination diet trial. If a cat has itchy skin, overgrooming, ear problems or repeated vomiting or diarrhoea, and other causes have been ruled out, the vet may suggest feeding only the trial diet for several weeks. If the signs clear, the old food is reintroduced to see whether they return. This is the only reliable way to diagnose a food allergy, since blood and saliva tests for it are not reliable.

The trial must be strict. No treats, flavoured medicines, table scraps or other cats' food can be allowed, or the result is useless. Do not start it on your own: ask your vet, who will check for fleas and other causes of itching first. Over-the-counter limited-ingredient foods are not a substitute, and some are not tested for hidden ingredients.

Last reviewed November 7, 2026

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Related terms

Prescription diet A food made to help manage a medical condition such as kidney disease or urinary crystals, fed only on a vet's advice. Grain-free Cat food made without wheat, corn, rice and other grains, which does not make it low in carbohydrate or better for most cats. Complete and balanced A pet-food label claim that a food supplies all the nutrients a cat needs at a stated life stage, when used as the only diet. Wet food Cat food sold in cans, pouches or trays, containing roughly 70 to 80 percent water, which helps a cat get more fluid. Overgrooming Licking, chewing or pulling at fur so much that it causes thin or bald patches, with causes ranging from skin disease to stress.