Atopy - Pet Hay Fever

What is Atopy?

Atopy, or Atopic dermatitis, is an allergic skin disease that causes itching. It is one of the two most common skin allergies in dogs and cats, along with flea allergy dermatitis.


Sometimes, our pet’s immune system can "overreact" to foreign substances (allergens or antigens) in the environment. Typical Atopy-causing allergens include pollens (from grasses, trees and weeds), dust mites and moulds. It was thought these allergens were inhaled (similar to asthma in people). Nowadays it’s noticed absorption of allergens can occur through the skin, especially skin in closest contact with the ground e.g. in between the toes (causing feet licking), under the armpits and groin (causing licking or biting) and even the skin around the bottom where they sit on the ground (causing "scooting" - dragging the bottom along the ground). It is also thought Atopy is inherited and may be either seasonal. Year-round allergy is more likely to be food allergy, which has identical symptoms to Atopic dermatitis, although is far less common.

It is common for animals to be allergic to more than one thing, which can make diagnosis an ongoing process. Atopy will usually get worse every year, and a seasonal allergy CAN develop into a year-round problem. However, sometimes a change in environment may kick start Atopy. Equally a change in address (moving to a new yard), can cure an Atopic pet by removing the causative agent. Given the recent floods in our area, a change in microbial environment may point to a rise in cases during the first half of 2011. Certainly a spike in the number of cases we have seen in the last 4 - 6 weeks indicates a local source has released heaps of pollen recently.


Atopic pets will usually target the feet with the fur on the top stained brownish with saliva. Also, skin around the bottom, armpits and tummy (where little hair grows) can be given attention licking and chewing. Initially this is a low grade itch, and pets will only lick in the evening when they begin to settle for the day. Later as the rash and dermatitis progresses, they can stop what they are doing and lick and scratch anytime. Eventually, scratching, chewing and licking will cause redness, hair loss, dry flaky skin and a variety of other signs.

Dogs can rub their face on the ground, and shake their heads with red, irritated ears. Frustratingly, examination of these ears often reveals no infection, just mild redness, yet the pet's are often really irritated. Within 1 - 3 weeks however, these ears - if no treatment is offered - become inflamed, infected and irritated. So we normally start treatment before the ears become infected.

Cats with Atopy will commonly lick themselves, although their owners will not always see this as abnormal, until the typical signs of hair loss and/or raw, inflamed skin lesions appear. Multiple small scabs over the body and rubbing of the face, neck and ears may also be seen. Excess fur in the vomit or faeces may indicate over grooming.

The first signs of Atopy are usually seen between 1 and 3 years of age, though this is variable. In puppies or young dogs with severe skin itch, particularly targeting the front of the thighs and stifles, food allergy should be considered. Older dogs can develop Atopy, particularly if they have been introduced to a new environment.

Bacterial and yeastInfections often result from the constant biting and scratching and make the problem much worse. So if you are seeing your pet doing a little too much scratching and biting, please come and see us.


Diagnosis depends on careful consideration of all the presenting signs and ruling out all other diseases that could be causing symptoms. Other diseases that could cause pruritus include fleas, mites, bacterial and fungal infections, and food allergies. It is important to understand the idea of “the itching threshold". A certain number of allergens may be well tolerated by your pet, and cause no signs of disease. But a small increase in the allergen load, may be enough to take your pet 'over the edge'. Other factors such as some fleas or a mild infection, stress or boredom may be enough to initiate itching and other clinical signs.

Diagnosis may involve some or all of the following:

  • Detailed History is very important. We need to know when the problem started, when it is at its worst, what treatments have been used before, etc.

  • The more information you can give us, the better we will be able to correctly diagnose the problem.

  • Examination.

  • A very close-up look at the skin - looking under the microscope for signs of bacterial or fungal infection.

  • Skin Scrapings to look for mange mites.

  • Plucking hairs - for mites or fungi

  • Trial therapy for Flea Allergy or Sarcoptic Mange

  • Trial therapy with antibiotics or antifungal drugs

  • Elimination Diet Trials to test for food allergy.

  • Intradermal Skin Test - to find out what allergens your pet reacts to. Small extracts of various allergens are injected into the skin, and reactions are observed. Blood Allergy Testing may be an alternative if intradermal testing is not possible. Referral to specialist dermatologists are available.

Some of these tests may need to be done more than once before a final diagnosis is made, or repeated later during the course of the disease.


There is usually no complete cure, but most cases can be successfully controlled. There are numerous options available, and possibly the best result will be achieved with a combination of treatments. Given the various known causes for Atopy, we work with your pet’s particular case in coming up with the most practical treatment plan.

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