Food Allergy in Dogs & Cats: Only an Elimination Diet Can Diagnose It

Cutaneous food allergy is an immune-mediated reaction to proteins in food — different from simple gastrointestinal food intolerance. Pets can develop allergies to foods they have eaten for years. The condition is not contagious and is distinct from food poisoning.

⚠️ Critical misconception: Blood tests, saliva tests, and hair analysis cannot diagnose food allergy. The only reliable diagnostic method is an elimination diet trial.

Signs in Dogs

• Itching of the paws, ears, face, or abdomen
• Recurrent skin infections and ear infections
• May be accompanied by vomiting or diarrhoea

Signs in Cats

• Excessive scratching of the head and neck; self-induced hair loss from over-grooming
• Miliary dermatitis
• Eosinophilic plaques or lip ulcers (indolent ulcers)
• May be accompanied by vomiting or diarrhoea

Note: These signs overlap significantly with other allergy types — symptoms alone cannot identify the allergen.

What Causes Food Allergy?

Pets are allergic to a specific protein (such as chicken, beef, or fish) — not to an entire brand of food. "Grain-free" diets are not guaranteed safe for an elimination trial. Standard "skin-formula" diets are not appropriate for a medical-grade elimination trial.

Diagnosis: The Elimination Diet Trial

Your vet will select a Hydrolysed diet (proteins broken down into fragments too small for the immune system to recognise) or a Novel protein diet (a protein source the pet has never eaten). Trial duration: approximately 8 weeks. Diagnosis is confirmed when symptoms improve and return when the original food is reintroduced.

Home Care During the Trial: Give only the vet-prescribed diet and plain water. Strictly avoid: 🚫 Any treats, 🚫 Table scraps, 🚫 Bones or leather chews, 🚫 Food belonging to other pets. Inform your vet if flavoured medications are needed.

Long-Term Management: Lifelong avoidance of the offending protein; complete, age-appropriate diet; treat any secondary infections concurrently.

When to Seek Urgent Care: Cat refusing to eat (urgent — prolonged fasting risks hepatic lipidosis); persistent vomiting or diarrhoea; facial swelling or difficulty breathing — emergency.

Contact Thonglor Pet Hospital

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