Understanding Pet Allergies: Symptoms, Types & What To Do
Dr. Sarah Jenkins
DVM, MRCVS · Omelo Vet
Allergies in pets are more common than most owners realise, and they're frequently mismanaged or under-diagnosed. Understanding the three main types of allergies - environmental (atopy), food allergies, and flea allergy dermatitis - is the first step toward effective management.
**Environmental Allergies (Atopy)**
Atopic dermatitis is the most common type of allergy in dogs and a significant issue in cats. The immune system overreacts to inhaled or contact environmental allergens: pollens (grasses, trees, weeds), house dust mites, mould spores, and sometimes human dander. Typical presentation includes:
- Recurrent ear infections (otitis externa)
- Red, inflamed skin (erythema) with secondary bacterial or yeast infections from constant scratching
- Seasonal pattern (though many dogs eventually become year-round as they sensitise to more allergens)
- Often begins between 1–3 years of age
Diagnosis is typically made by excluding other causes (especially food allergy and fleas) and confirmed by intradermal skin testing or serology. Treatment options include allergen-specific immunotherapy (ASIT - the only treatment that modifies the underlying immune response), Cytopoint injections (monthly anti-IL-31 antibody), Apoquel (daily anti-itch medication), and corticosteroids (useful short-term but with significant long-term side effects).
**Food Allergies**
True food allergies (as opposed to food intolerances, which cause primarily gastrointestinal signs) cause immune-mediated reactions to specific protein sources. Common culprits include beef, chicken, dairy, wheat, and eggs. Symptoms overlap significantly with atopy: skin itching, ear infections, and sometimes vomiting and diarrhoea.
Diagnosis requires a strict elimination diet trial of 8–12 weeks using either a novel protein source (a protein the pet has never been exposed to) or a hydrolysed protein diet (where the protein molecules are broken down so small the immune system can't recognise them). No treats, flavoured medications, or supplements during the trial. This is the only reliable way to diagnose food allergy.
**Flea Allergy Dermatitis (FAD)**
The most common skin disease in cats and very common in dogs. An allergic pet only needs a single flea bite to trigger an intense reaction - the allergy is to proteins in flea saliva. Signs include intense itching at the base of the tail, thighs, and abdomen; hair loss and hot, inflamed skin in these areas; and the presence of flea dirt (comma-shaped black specks). Management requires year-round, veterinarian-recommended flea prevention on all pets in the household.
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