Allergies in animals

Animals have a similar range of cells, antibodies and receptors as humans. It is therefore unsurprising that they too increasingly react to pollen, house dust mites etc. However, non-allergic reactions are more common than allergies.

Like humans, animals such as dogs, horsese and cats may also suffer from different forms of allergy and non-allergic hypersensitivity reactions. How this comes about is still not fully understood. It is assumed that an interaction between genetic components and environmental factors is involved.

Dogs

Triggers

The main triggers of adverse reactions in dogs are:

• fleas,
• dog food ingredients (beef, poultry, eggs, maize, wheat, soya and cow milk) and
• allergens in the environment such as pollen, mould and house dust mites.

Symptoms

The symptoms vary depending on the trigger. With fleas, dogs react to the flea bites or more precisely to the saliva of these tiny parasites.This causes marked itching, primarily at the base of the tail.

If the symptoms are caused by allergens in the environment, they are often seasonal. Pollen does not usually lead to runny nose but instead to canine neurodermatitis – a form of atopic eczema. It manifests as redness and itching, mostly on the ears and paws. With dogs, an allergy to mould and house dust mites can cause runny nose as well as atopic eczema.

Severe allergic reactions to dog food ingredients are rare in dogs. It is more often a case of hypersensitivity or intolerance. Typical symptoms are vomiting and/or diarrhoea but may also include skin reactions.

With a house dust mite allergy, the same measures help as with humans: vacuum clean often using a HEPA filter, wet mop the floor regularly, ventilate the home well two or three times a day for 5 to 10 minutes, cover the dog bed with an encasing ideally made with textiles that are washable at 60oC, do not let the dog enter bedrooms, as the concentration of house dust mites is at its highest in beds.

Diagnosis

Skin and blood tests are used for the diagnosis of an allergy in dogs. In the case of an allergy to dog food, an elimination diet is followed to identify the trigger.

Treatment

Treatment is similar to that for humans: avoid the substances that trigger the allergy to reduce exposure. As avoiding the triggers is usually not enough in itself, medication such as antihistamines or cortisone is also used. In some cases, desensitisation may also help.

Facts and figures

• One in five dogs suffer from an allergy or intolerance
• West Highland white terriers, boxers, French bulldogs, Vizsla (Hungarian pointers), bull terriers and Rhodesian ridgebacks are at increased risk of pollen allergy.

Cats

Triggers

In the case of cats, flea bites are one of the most common triggers. Cats have a reaction to the saliva of the flea, causing skin symptoms.

Other common triggers are:

• pollen
• house dust mites
• mould
• dead skin cells from other animals
• cat food ingredients
• fragrances
• care products
• polishes and detergents
• textiles
• rubber and plastic materials
• medication
• cigarette smoke.

A feature peculiar to white cats: they are hypersensitive to sunlight. The ears are primarily affected. The sun can damage the thin, poorly pigmented tissue or cause the tissue to die (necrosis).

Symptoms

Cats react with different symptoms. The most common are:

• itching, frequent scratching or cleaning (inflamed areas of skin)
• coughing, sneezing, wheezing
• eye discharge
• vomiting and diarrhoea
• itching in the ears and ear infections
• inflamed throat and snoring
• swollen paws and licking paws

Diagnosis

Skin and blood tests are used for the diagnosis of an allergy in cats. In the case of an allergy to cat food, an elimination diet is followed to identify the trigger.

Treatment

Treatment is similar to that for humans: avoid the substances that trigger the allergy to reduce exposure. As avoiding the triggers is usually not enough in itself, medication such as antihistamines or cortisone is also used. In some cases, desensitisation may also help.

Facts and figures

• Approx. 6% of cats with skin problems have an allergy-related cat food intolerance.
• Abyssinian and Devon Rex cats are at greater risk of developing an allergy.

Horses

Triggers

Horses most commonly suffer from equine asthma, which in its milder form is known as inflammatory airway disease (IAD). The mechanism underlying the disease is not yet fully understood.

Summer eczema is caused by an allergic reaction to the saliva of certain insects.

Other triggers are:

• insects (especially gnats and flies)
• aseroallergens (allergens in the air)
• grass, tree and weed pollen
• dust mites
• mould spores

Contact allergens (rare):

• plants
• care products, medication (shampoos, ointments)

Feed allergens (rare):

• Certain types of hay, concentrated feed, supplements

Symptoms

The symptoms vary depending on the disease. A typical first sign of equine asthma is occasional expectoration when first setting off. However, as the disease progresses, respiratory function is impaired, with spasmodic bouts of coughing and whitish nasal discharge and possibly respiratory distress. A pollen allergy can cause urticaria, itchy eczema and recurrent airway obstruction (heaves).

Typical symptoms of summer eczema are:

• marked itching in specific places, primarily along the abdomen and under the belly, on the mane and on the dock of the tail
• rash
• itching
• irritation of the eyes and nostrils (conjuncitivitis and rhinitis)

Diagnosis

As with cats and dogs, the diagnosis of an allergy in horses is based on the presenting symptoms and by excluding other possible causes. If an allergy continues to be suspected, skin and blood tests are used. For an allergy to horse feed, an elimination diet is used to determine the trigger.

Treatment

Treatment is similar to that for humans: avoid the substances that trigger the allergy to reduce exposure. If this is not possible, medication is used. In some cases, desensitisation may also help. In cases of insect venom allergy, insect repellents can be used to ward off the insects. Use can also be made of full body blankets to protect horses from the insects.

Facts and figures

10% of all horses suffer from summer eczema.

Anaphylactic reactions

Potentially life-threatening reactions are very rare in animals. They may be triggered by wasp and bee stings, animal feed and medication.

NB: In Switzerland, the most common cause of poisoning in animals is human medication. Do not give any human medication without first consulting a qualified vet.

Diagnosis

The first steps are taking an accurate medical history, evaluating the symptoms and excluding other possible diseases.This may be followed by skin and blood tests. If an animal feed intolerance is suspected, diagnosis is usually made using an elmination diet, which involves the removal of the suspected feed ingredient from the animal feed for a defined period.

Treatment

• The most important therapeutic approaches are:
• avoiding the allergen, where known and possible
• allergen-specific immunotherapy
• drug treatment
• new treatment approaches such as immunisation

Editors: aha! Swiss Allergy Centre in co-operation with the Scientific Advisory Board.