The diagnosis of allergies can be complex and require several trials or tests. Some of these involve ‘home work’ and some testing in hospital. By far the majority of the allergy diagnostics can be undertaken at home.
 
In clinic diagnostic test:
  • Check for infection: secondary infection is common with allergies, but if not controlled, finding the underlying problem can be near impossible.
  • Check for microscopic parasites such as demodex or scabies mites.
  • Test for specific allergens via an intradermal skin test or a blood test. The skin test involves lots of little needles of allergens to the skin to see which ones swell and go red, while the blood test can measure IgE levels in the blood to various allergens. Where possible the skin test is considered the slightly better of the 2 tests, but is not available in all areas and can be affected by certain drugs.
Home work:
This should generally be undertaken in conjunction with the advice of a veterinarian to ensure it is done in a systematic manner.
  • Food allergy elimination trial- rule out food allergy as a cause of skin & ear problems.

Food allergies cannot reliably be tested for with blood tests. The best method is via a period of feeding a diet which has been determined to be hypoallergenic (something the pet hasn’t been exposed to before) and then rechallenging with individual proteins. When determining the hypoallergenic diet it is important that all regularly fed foods be considered, as many have ingredients, especially proteins in common, so merely changing brands will do little to achieve the end goal. Common hypoallergenic foods in Australia include fish and kangaroo as a protein source. Potato or tapioca are often used as a carbohydrate source. Overseas, lamb is commonly used, but in Australia lamb is widely eaten by most people and meat eating pets so it is not suitable. Some foods maybe labelled as ‘for sensitive skin’. There are many different types of these, and many are not suitable for an initial diet trial. They often contain a single protein source, which is great if you have determined that protein source is safe for your pet, and may also contain added extras such as omegas. The omega 3 and 6 fatty acids are not overly useful as a sole therapy in skin disease management but do have some anti-inflammatory effects on the skin by inhibiting small sectors of the complex allergy pathway in the body, and can be helpful for some pets.

  • Isolation trial. A dog should be bathed and then kept away from grass/plants for about 48 hours, then re-exposed to grasses and plants. If in the time off the grass the skin settled, and it deteriorated when re-exposed a contact allergy is likely. The more severe the problem the longer the period the skin may take to settle when removed from the allergen. The bath is used to remove pollens and other allergens from the coat, so they do not continue to cause problems during the test period. If the skin is severely infected then this can complicate the interpretation of results.
  • Flea trial- excellent flea control is important in all allergic cats and dogs, however some are particularly sensitive and a single flea once every few weeks can continue to cause itch long after it is gone. Implementing a very strict effective flea control regime can help to determine is fleas are an important part of the skin disease. Itchy animals will often groom fleas away during their ‘chewing’ and many pet owners are unaware of the problem.
  • General skin hygiene: regular bathing in soothing or antibacterial and antifungal shampoos and conditioners can be an important part of controlling allergies, in many cases this dramatically reduces or eliminates the need for stronger drugs.