Mar Vista Animal Medical Center

3850 Grand View Blvd.
Los Angeles, CA 90066

(310)391-6741

www.marvistavet.com

AIRBORNE ALLERGIES (ATOPIC DERMATITIS)

Every one knows someone with “hay fever.” Airborne pollens, molds, dust particles, etc. are inhaled and soon the sneezing and sniffling begins. A simple way to think of atopy for pets would be simply saying that the airborne allergen is inhaled by the pet but instead of sneezing and sniffling, the pet gets itchy skin. In fact, this was what we thought was happening for many years but the situation turns out more complicated. Airborne pollens, molds, dust particles etc. gain entry to the skin through a defective skin barrier and from there their proteins are presented to the immune system. Cells of inflammation migrate back to the skin and soon the itching and scratching begins. The allergens come from the air but the itch is manifested in the skin.

Airborne particles (pollens, danders etc.) are harmless to someone who is not allergic to them.
Allergy develops in individuals who are genetically programmed to do so.

Breeds predisposed to develop atopy

Dalmatian
(Photocredit: MorgueFile.com)

Golden
Retriever
(Photocredit: MorgueFile.com)

West Highland
White Terrier

Shar Pei

Labrador
Retriever
(Photocredit: MorgueFile.com)

 

 

 

 

 

Cairn Terrier
(Photocredit: Kathrin Albrecht via Wikimedia Commons)

Lhasa Apso
(Photocredit: MorgueFile.com)

Shih Tzu
(Photocredit: MorgueFile.com)

Boxer

Pug

 

FEATURES OF ATOPY

There are many reasons for pets to itch: parasites, allergy to flea bites, food allergy, secondary infection and the list goes on. The following are findings in the history and examination of the patient that might lead to a diagnosis of atopy. (In fact, meeting 5 criteria from this list yields an 85% accuracy for the diagnosis of atopic dermatitis, at least for dogs:

  • Young age of onset

    Seasonal itchiness due to atopy tends to begin early in a pet's life (between ages 1 and 3 years in 70% of dogs diagnosed with atopy). Food allergy tends to begin later (more like age 5 or 6 years in dogs) or earlier (less than 6 months of age). Age at which itching first manifests is not as reliable a sign in cats as in dogs.

  • Mostly indoor lifestyle

    It is indoors where many airborne allergens concentrated; however, it is important to note that allergens in the air are in the air for miles it is not easy to escape allergens by simply going outdoors nor by simply going indoors.

  • Good response to steroids

    Whether the patient is a dog or cat, itchiness due to atopy responds rapidly to cortisone-type medications (prednisone, depomedrol, dexamethasone, etc.) as does itching due to insect bite allergy. Food allergy is more variable in its response; it may or may not respond well.

  • Chronic or recurring yeast infections in the skin

    Yeast (Malassezia pachydermatis) live on the surface of the skin normally but with all the changes allergy causes to the microenvironment of the skin, yeast will proliferate and create a stinky, thickened, pigmented skin that resembles elephant skin or even tree bark. Environmental allergy is a strong predisposing factor in the development of yeast dermatitis. For more information click here.

  • Front feet involved
    Ear flaps involved
    There is a lesion distribution that is common in inhalant allergy. It is, unfortunately, very similar to that of sarcpotic mange and overlaps greatly with the lesion distribution of flea bite allergy.

  • Ear margins not involved
    Ear margin involvement is suggestive of sarcoptic mange and would lead one away from airborne allergies.

 

A few reactive blebs on an intradermal skin test

  • Lower back area not involved
    The lower back is the flea bite zone (frequently called a "California Wedge"). There are very few conditions other than flea bite allergy that cause itching in this area so if this area is involved, one must make sure flea control is achieved before further evaluating the skin.

    Seasonality of the itching is also a clue towards an airborne-related allergy but since there are many climates where seasons are ambiguous, this is not necessarily a hard and fast feature of atopic dermatitis. It should also be noted that, while skin testing and blood testing are used to make immunotherapy sera for treatment of atopic dermatitis, reactions and positive results on these tests do not contribute to making a diagnosis of atopic dermatitis. Many normal animals will have positive results. These tests are for animals where the diagnosis of atopic dermatitis has already been made based on the above criteria as well as ruling out other itchy diseases.

It should be noted that food allergy, which is best thought of as a special form of atopic dermatitis rather than as a separate disease, presents with a very similar irritation pattern but a different history. Sarcoptic mange also has a similar itch pattern. (original graphic by marvistavet.com)

 

In cats, the irritation pattern is not as characteristic. There are four common manifestations of atopy:

Non-lesional fur mowing
(original graphic by marvistavet.com)

Eosinophilic Granuloma Complex
(original graphic by marvistavet.com)

 

 

Miliary Dermatitis (small seed-like scabs)
(Photocredit: CarolDermoid via Wikimedia Commons)

Face and ear itching

Unfortunately, these same irritation patterns can be found in numerous other skin conditions and, in fact, up to 25% of atopic cats have multiple types of allergies.


(Photocredit: Morguefile.com)

While it would be nice to have a blood test that could tell us if a pet’s itching is due to atopy, it is important to realize that such a test does not exist. Atopy remains a “clinical diagnosis” which means the diagnosis is made based on history and examination findings.


(Photocredit: Morguefile.com)

 

TREATMENT OPTIONS

Clearing Secondary Infections

Before doing anything else, it is important to clear up secondary infections. Secondary infections involve bacteria (usually Staphylococcal) and/or yeast (Malassezia) at the site of the itchiest areas on the body. These organisms live naturally in the skin but when the skin is irritated, they gain access to inner tissue layers and proliferate. Sometimes they actually come to generate further allergic response in the skin. These infections tend to be recurrent and are the usual cause of recurrence of itch symptoms in a patient previously controlled.


Dog with yeast dermatitis
(Photocredit: CarolDermoid via Wikimedia Commons)

 Many patients will not be particularly itchy in between infection flare-ups so it is especially important that these be controlled.

Hyposensitization (Allergen Specific Immunotherapy)

Hyposensitization, more commonly known as "allergy shots," is by far the treatment of choice of atopic dermatitis. All the other medications are basically just itch relief; only hyposensitization actually changes the immune system. Some dogs are eventually able to go off all treatment and are no longer allergic after they have been on hyposensitization long enough. Most dogs are at least much better and require fewer additional treatments.

  • Allergy shots require approximately 6-12 months to begin working.
  • 25% of atopic dogs will not respond (these are usually the animals allergic to multiple allergens.)
  • 25% will require prednisone or similar steroid at least at some times.
  • You will most likely have to give the allergy shots yourself.
  • Referral to a veterinary dermatologist will likely be necessary.

In hyposensitization the patient is injected with small amounts of allergens on a regular basis. As time passes, the amounts of allergens increase and injections are given at longer intervals. The selection of allergens is made based on the results of either an intradermal skin test (as described above), an “in vitro” test (a blood test) or a combination of the results of both tests. The younger the pet when this treatment starts, the better it works. For more details on allergen specific immunotherapy click here.)

Steroid Hormones

These cortisone-type medications (prednisone, prednisolone, triamcinolone, dexamethasone etc.) tend to be useful as the "first line of defense" against itchy skin. A higher dose is used at first but this is quickly tapered down once the condition is controlled. Prednisone, for example, is given every other day so as to allow the pet one day of recovery from the prednisone's hormonal actions. An atopic pet will usually respond within days.
Side effects include:

  • Excess thirst
  • Excess hunger
  • Excess urination (which could lead to house-breaking issues)
  • Suppression of the immune-system/bringing out latent infection (especially urinary tract infection and upper respiratory infection.)
  • Raising blood sugar/destabilizing a borderline diabetic (especially a problem for cats if long-acting injectable steroids are used). In the short term, side effects can be controlled by adjusting dosage but in the long term, these medications are more problematic and if possible their use should be minimized.

Steroid hormones are very useful for acute flare-ups as well as for long term management of atopic dermatitis (assuming limits are placed on how long they are used).

Cyclosporine

Cyclosporine is a modulator of the immune response that has been very helpful in organ transplant patients both human and non-human. It has been found to be reliably effective in atopic dermatitis and does not carry the unpleasant side effect profile that steroids do. That said, it is not without side effects of its own. It is used mostly in dogs but can also be used in cats. It is for long term management and is not helpful for acute flare up control. For more details on this medication click here.

Oclacitinib

This is a new medication best used for itch relief and blocking itch symptoms. It has been especially popular as it works very fast. It does not address the inflammation in the skin; it just stops the itch sensation. This means that infection still needs to be controlled. For more details visit: www.Apoqueldogs.com

Canine Atopic Dermatitis Immunotherapeutic (Cytopoint®) Injections

This is a new treatment which uses vaccine technology to eliminate one of the main mediators of itch sensation. The injections provides relief from itching for 1 month in 80% of dogs and show effectiveness usually within 24 hours of the injection. For many dogs, relief of itch stops the vicious cycle of itch/infection. Again, infections, if present, still need treatment but the sensation of itch is usually controlled.

Proper Coat Hygiene/Removing Allergens From the Environment If Possible

  • Bathing the pet weekly to remove allergens from the fur may be helpful in reducing allergen exposure plus tepid water is soothing to itchy skin. There are also many therapeutic shampoos that can be used to restore the skin’s natural barrier or to assist in general itch relief. For more details, see our section on Itch Relief.
  • Avoid stuffed toys, wash bedding regularly. This minimizes dust mite exposure. Also, remove the pet from the area when vacuuming or dusting.
  • Use air-conditioning and/or an air filter system.
  • Keep the pet away from the lawn while it is being mowed.
  • Minimize houseplants.

 

Omega 3 Fatty Acid Supplements

These products are NOT analogous to adding oil to the pet's food. Instead, these special fatty acids act as medications, disrupting the production of inflammatory chemicals within the skin. By using these supplements, it may be possible to postpone the need for steroids/cortisones or reduce the dose of steroid needed to control symptoms. It takes a good 6 weeks to build up enough omega 3 fatty acids in the body to see a difference.

Antihistamines

Antihistamines have been popular for many years for pets, it seems their effectiveness does not stand up to scrutiny. They do not provide either short term relief nor reliable long term relief. They may be helpful in combination with other products in that their use may reduce the need for other products. They may work better in cats than in dogs.

Solid Flea Control

Allergies are additive. This means that when a patient has multiple allergies, each allergy alone may not be enough to cause itching but the allergies all active together probably will. Consequently, taking away one of the active allergies may be enough to allergy reduction to resolve the itching. Flea bite allergy is extremely common. We now have so many effective products available that there is no reason for an animal to contend with a flea bite allergy. This simple bit of therapy (flea control) may be enough to bring the pet below his or her itch threshold without having to contend with any of the therapies listed above.

Itchy skin has been the scourge of dogs and cats for decades if not centuries. We are now armed with great understanding of immunology and have many tools to address allergy symptoms. Your veterinarian can guide you further with regard to a proper regimen or you may wish to consider seeing a veterinary dermatologist for more specialized guidance.

 

IS YOUR PET A CANDIDATE FOR SKIN TESTING?

Testing is best done during your pet's non-itchy season (if there is one) so that the skin responses of the test will not be clouded by active inflammation. The test involves injections of small amounts of allergen extracts into the skin. Reactions noted are compared to reactions produced by two controls: pure histamine (very inflammatory) and pure saline (very non-inflammatory).

In order for skin testing to be performed, medications must be discontinued well in advance. How long in advance depends on the medication and on the policies of the veterinary dermatology practice that will be doing the test. Oral steroids, for example, commonly require a full month discontinuance, which can be problematic if the pet is highly dependent on medication for life quality.

 

IN VITRO TESTING?

In vitro testing does not always require withdrawal of medications nor does it require referral to a specialist. There is no hair clipping and sedation is rarely necessary. Blood is simply drawn and checked for antibodies against common allergens for that geographic region. A profile is reported and allergens can be selected accordingly. It is important to remember that these results do not necessarily imply that the patient is allergic to substances reported; this is simply a test for antibodies. Antibody elevations are very common with levels changing based on an assortment of factors (whether the pet has parasites at the time of the test, how common the substances being tested are, how long medications have been used prior to the test etc.) and interpretation of the profile is part of the “art of veterinary practice.”

For more details on what is involved, see our page on Allergen-Specific Immunotherapy (Allergy shots).

To find a veterinary dermatologist in your area, visit the web site of the American College of Veterinary Dermatology at www.acvd.org.

Page last updated: 1/8/2019