Skin Allergies in Dogs and Cats

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Bakers Hill Veterinary Hospital
4609 Great Eastern Highway
Bakers Hill
WA 6562

08 9574 1061

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Living with an itchy pet can be an extremely frustrating experience for you as well as being distressing for your pet.  Persistent scratching and chewing by the pet can result in self-trauma, leading to wounds and infections.  The following information is intended to provide you with a basic understanding of the most common underlying causes of itching and allergies in cats and dogs.

The Most Common Causes of Itching

The common causes of itching fall into two groups: external parasites and allergies.  External parasites that most commonly cause chronic itching include fleas and sarcoptic mange (mites).  We often recommend therapeutic trials for fleas and sarcoptic mange in chronically and severely itchy dogs and cats.  We always recommend stepped-up flea control and monitoring for fleas, as flea infestation can make other allergies much worse.

What are Allergies?

An allergy is a state of hypersensitivity in which exposure to a harmless substance, known as an allergen, causes the body’s immune system to “overreact”.  People with allergies usually have what we call “hay fever” (watery eyes, runny nose and sneezing) or asthma. While dogs can occasionally also have respiratory allergies, more commonly they experience the effects of allergies as skin problems.  Though there are a variety of presentations, this can often be seen as redness and itching, recurring skin or ear infections, and hair loss. 

What are the Major Types of Allergies in Dogs?

Flea Allergy


Flea allergy dermatitis is the most common skin disease in dogs and cats.  For the flea allergic patient, consistent year-round flea control is essential, not only for the patient, but for all pets in the household. You may not see fleas, but that doesn’t mean they aren’t there, as fleas only spend 5% of their life-cycle on your pet, the rest of the time is spent in the environment. Furthermore, the allergy is caused by the flea’s saliva, and it only takes a few bites to induce the problem.  Finally, the itchy pet often scratches so much that adult fleas are removed, making them hard to find. 

Because flea allergy is so common, we recommend that complete flea control be instituted before proceeding with diagnostics for other allergies and that year-round flea control be maintained for all allergy patients.

Food Allergy

Some pets develop specific hypersensitivities to components of their diets.  The allergen usually is a major protein or carbohydrate ingredient such as beef, lamb, chicken, pork, corn, wheat, dairy and soy.  The diagnosis of food allergy involves testing your pet by feeding a special diet, called an elimination diet, that contain only ingredients that the dog or cat has never eaten before. This is often achieved by feeding a prescription diet, such as Hills z/d Ultra, for a period of 8-12 weeks. A home cooked diet of a novel protein (eg kangaroo, camel, goat, horse meat) and novel carbohydrate (eg sweet potato, lentils) can also be used. If the signs resolve, a challenge is performed by feeding the former diet and watching for a return of the itching.  If this occurs, a diagnosis of food allergy is confirmed. 

Atopic Dermatitis

Atopic dermatitis or ‘atopy’ is an inherited allergy to normally harmless substances including the pollens of weeds, grasses and trees, house dust mites and mould spores.  Diagnosis of atopy is made based on the results of intradermal skin testing or by a blood test.  Evaluating the results of these tests helps us compile a list of allergens for a “vaccine” to decrease the pet’s sensitivity. This is called “desensitisation”. Blood testing can be done at Bakers Hill Veterinary Hospital, however intra-dermal skin testing must be done by a specialist dermatologist. Sometimes the diagnosis of Atopy is assumed after ruling out the other major types of allergies. This is often done when we decide together to control the allergy, rather than going down the desensitisation path.

Atopy is an inherited disease, so it is recommended to not breed from affected dogs and cats.

Secondary Infections

Allergies are often the underlying cause of recurring skin and/or ear infections.  Bacterial and yeast infections, though secondary to the allergy, can cause an increase in your pet’s level of itching. We collect samples which are examined under our in-house microscope to diagnose infections in your pet.

Medications used to Stop the Scratching

With all allergies, rather than just treating the scratching, it is more effective and safer for your animal to go through the process of finding out what your animal is allergic to, so it can be avoided (in the case of food allergies), treated (in the case of fleas or mites) or the pet can be desensitised (in the case of atopy).

Symptomatic drug therapy can help to reduce itching in allergic dogs.  The main drugs we use are prednisolone/cortisone (steroids), cyclosporine and antihistamines. Regular health checks and blood tests are strongly recommended if this treatment is used to control your pet’s allergies to ensure your pet does not suffer any side effects from the medication. With all medication, especially steroids, we try to use the lowest dose of the medication possible that still controls the animals itching. This is the reason that we encourage diagnosis of the underlying cause of the allergy so that more specific, or less potentially harmful treatments, can be instigated.

Adjunct Therapies

Some other things that have been proven to make a difference for the allergic pet (and are always worth trying) include:

  • Oatmeal shampoo & conditioner (especially the “leave on” type) – proven benefit to improve the skin’s ability to defend itself against the allergen if done twice a week
  • QV oil 40 ml in 1 L of water – spray on skin twice a week
  • Fish oils – 1 capsule per 10 kg – benefits after 8-10 weeks

Can Allergies be Cured?

Unfortunately, there is no cure for allergies and it is usually a life-long problem. We seek to control allergies with desensitisation, avoidance or symptomatic treatment and improve the quality of life for both you and your pet.  Together we will formulate the best program of management that suits all involved with your pet’s care.