Allergy in companion animals
Allergy is a complex condition
Allergy is a genetically predisposed condition of hypersensitivity to substances that are common and harmless to most animals. The immunological mechanisms underlying allergy in dogs, cats and horses are essentially the same as in humans. There are five main types of allergy:
- Atopy or atopic dermatitis: Hypersensitivity to pollen, mites, moulds and dander
- Food allergy: Hypersensitivity to protein components of the diet, such as chicken
- Insect and flea allergy: Hypersensitivity to insect and flea saliva
- Contact allergy: Hypersensitivity to materials such as plastic, linoleum and paint
- Drug allergy: Hypersensitivity to antibiotics, antiparasitic and other medicines
Hypersensitivity is caused by a dysfunction in the animal’s immune system whereby the immune system incorrectly perceives a harmless substance as harmful. When an animal is in contact (physically or through inhalation or ingestion) with an allergen for the first time, its immune system will react by producing IgE antibodies. These antibodies are specific for a particular allergen. When the animal encounters the allergen again, the allergen will be presented to a mast cell which is already connected to allergen-specific IgE. This leads to the production and release of undesirable inflammatory mediators such as histamine and cytokines.
Pruritus is an essential feature of allergy – its diagnosis therefore requires a history of itching. Cutaneous lesions such as erythema, excoriations and self-induced alopecia also relate to the severity of the disease. Respiratory symptoms (allergic rhinitis, asthma), gastrointestinal symptoms (vomiting, diarrhoea, gastritis) and ocular symptoms (conjunctivitis) may also appear. Reduced quality of life – for both pets and owners – is an outcome that has an impact not only on the health and wellbeing of the pet, but also on the human–animal bond.