Allergic skin disease

Allergy is a common cause of skin disease causing itchiness in dogs and cats. Atopic skin disease is one common type of allergy and a reaction by an individual animal to environmental aeroallergens such as pollens from grasses, weeds, trees, mould spores and house dust mite.

An adverse food reaction is a reaction by an individual to a particular food substance. The most common causes of adverse food reactions in dogs are caused by proteins and carbohydrates such as beef, mutton, chicken, wheat, corn, soy, dairy foods and eggs.

The most common causes of adverse food reactions in cats are fish, beef and dairy products.

Symptoms of allergy

• The most common clinical sign of allergy is itching, most commonly involving the muzzle, around the eyes, ear flaps, armpits, groin and paws. Some dogs may have recurrent ear infections.

• As a result of chewing, licking, rubbing and scratching the skin becomes inflamed and prone to secondary infections with bacteria and yeast. In dogs with chronic disease there is often hair loss and the skin becomes thickened, scaly and black.

• The hair coat may feel greasy and be associated with an offensive odour. Occasionally dogs and cats with adverse food reactions may have loose stools or diarrhoea.

Diagnosing allergic skin disease

Intradermal allergy test:

• The best way to identify a specific allergy to pollen, dust, mould or insects is to perform an intradermal allergy test.

• This involves clipping a patch of hair from the side of the flank and pricking the skin with a tiny amount of purified allergen extract. A positive reaction is a raised swelling observed thirty minutes after intradermal injection.

• The skin test is affected by a number of drugs including antihistamines and corticosteroids. As all cortisone tablets, injections, lotions, eye and ear drops interfere with the skin test, it is important that your pet is withdrawn from treatment prior to testing.

Serological (blood) allergy testing:

• More recently we have been performing serological (blood) allergy testing in dogs with pollen, mould and dust allergies in conjunction with skin testing.

• We believe that by combining the results of the skin and serological testing that we can develop the most optimal allergy profile for your pet. This increases our chances of successful vaccine immunotherapy (desensitization).

Skin and blood testing are not useful for the diagnosis of adverse food reactions in dogs and cats. The diagnosis is made by an elimination diet trial which involves feeding a protein and/or carbohydrate source that your pet has not received before for a period of six weeks. The choice of diet is very important and the veterinary dermatologist can guide you with the appropriate diet selection.

Allergy treatments

There are several different ways allergy can be managed in order to keep your dog or cat comfortable.

Allergen specific immunotherapy with an allergy vaccine is the preferred method of treatment for canine and feline atopic dermatitis and involves using a vaccine that is made specifically for your pet on the basis of the skin and serum allergy test results.

It is important to remember that improvement with allergy vaccines is gradual with obvious benefit taking between six to twelve months to appear.

Dogs and cats with adverse food reactions must receive a modified special diet.

How successful are allergy vaccines?

Allergy vaccines are successful in approximately 70% of dogs and cats with environmental allergic skin disease.

The vaccine needs to be used for 12 months before we can evaluate whether is has been successful in reducing the itching.

If a dog or cat responds to the allergy vaccine then it will need to continue the vaccine for between three to five years. Some dogs and cats require allergy vaccine for a lifetime.