Allergies & Itchy Skin

Cannington Veterinary Hospital - Dog scratching

Itchy skin is one of the most common medical problems we see in dogs.  It can also be one of the most frustrating for dog, owner and veterinarian alike.  Although the symptoms may appear very similar there are actually many different causes of itchy skin. Many owners, because of the constant and ongoing nature of the problem, conclude that the dog is scratching out of habit, but this situation would in fact rarely if ever occur.


The most common cause of itchy skin in dogs is allergy but there are also a significant number of cases that are due to parasitic, bacterial or fungal organisms.  Although most dogs with allergic dermatitis will get relief with anti-allergy medication the same medication can actually aggravate some of these other causes. For this reason it is important that the vet is able to examine the dog and obtain a full history of the problem before medication is dispensed. In many cases simple laboratory tests such as skin scrapings may be required to help confirm the diagnosis.

The vast majority of itchy dogs however suffer from allergies.  Although medication will usually provide short-term relief it must be remembered that this is only treating the symptoms and the effects will only last while the medication is being given.  In many cases cortisone type drugs are the only things that will give relief and although safe when used correctly, it is well established that prolonged use of this type of medication can have adverse side effects.  Therefore for ongoing cases it is usually worthwhile trying to identify the specific cause of the allergy and hopefully eliminate it.

We most commonly see allergies caused by fleas. This is more than just having fleas; rather it is a severe sensitivity to the fleabite such that only one bite every few days can be sufficient to cause intense irritation. Until this is ruled out it is difficult to investigate other possible causes so the first step in trying to diagnose the itchy dog is commencement of an intensive fleabite prevention program. The simplest and most effective way of achieving this is a daily application of an appropriate insecticide such as Permoxin for a two-week trial period. To aid the diagnosis it is important that no other medication be given during this period. If a marked improvement occurs then flea allergy dermatitis is the likely cause.

Food, Contact & Inhalant Allergy

Other possible causes of allergic dermatitis include food, contact or inhaled allergens. Food allergy can occur at any age and in most cases is due to a protein that the pet has been exposed to continually over a period of time. For this reason any food the animal has been eating recently can be a potential cause even if they have eaten it for years without previous problem. Elimination diets such as rabbit and rice, or chicken and rice for a period of 4 weeks is required to rule this problem out.

Contact allergy tends to affect the lower body, particularly areas where hair cover is thin such as the abdomen and armpits. Confirmation of this problem involves isolation (at a hospital or boarding kennel) and then re-exposure to the environment.

Inhalant allergy or atopy requires special skin tests similar to the tests people have for hay fever and this is best performed by a specialist veterinary dermatologist. In summary, the itchy dog in most cases can get relief with correct diagnosis and treatment. This is best achieved through a logical, step-by-step approach including history taking, examination, laboratory tests and elimination of possible causes such as fleas. In the few cases where these steps have been followed and the problem has still not been resolved then referral to a specialist would be the next step.