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Overview
of Allergies in Dogs and Cats
Introduction
Allergies are abnormal reactions in which an animal’s immune
systems over reacts to everyday environmental substances.
These substances, called allergens or antigens, cause allergic
reactions upon exposure by inhalation, ingestion, or skin
contact. There are many kinds of allergens such as tree,
grass or weed pollens, molds, house dust, house dust mites,
animal dander, human dander, feathers, fleas, certain bacteria,
various chemicals and even ordinary foods.
Cause
The root cause of allergies is unknown, although there is
clearly a heritable, genetic basis to the problem. What ever
the cause, it is known that for some reason, allergic individuals
become sensitized to allergens by producing allergen-specific
antibodies against ordinary environmental substances such
as pollens and dust. These antibodies attach themselves to
Mast Cells in the skin and elsewhere in the body. Subsequent
exposure of the allergic individual to the offending antigens,
by inhalation, ingestion, or skin contact, leads to cross-linking
of the Mast Cell surface antibodies by the offending antigens.
Surface antibody cross-linking causes Mast Cells to release
histamine, enzymes, and many other biologically active chemicals.
These chemicals interact with each other and body tissues
to produce the symptoms we recognize as allergies.
Symptoms
Allergic pets manifest symptoms in one of several ways:
- Itchiness
and Scratching. The most common manifestation of allergies
among dogs and cats is excessive scratching.
This excessive scratching can be localized – affecting
just the feet, for example – or it may be generalized.
- Respiratory
problems. Less commonly, affected pets may show some
combination of coughing, sneezing, reverse sneezing
and wheezing. Red, itchy ears, runny nose, red eyes,
and watery eyes can also be seen. Stomach upset.
- Rarely,
allergic
pets may experience vomiting or diarrhea.
Diagnosis
The diagnosis of pet allergies depends on the type of allergy
present. There are five known types of allergies in the dog
and cat. Each of these requires specific diagnostic methods
and is briefly discussed below.
- Inhalant allergies. This
is the most common form of pet allergies. It is also referred
to as allergic dermatitis
or atopy. Affected pets typically lick, scratch and chew
to excess at the face, paws, arm pits, and groin. In the
early stages at least, the excessive scratching usually follows
a seasonal pattern and responds well to cortisone type medications.
Inhalant allergies can be diagnosed by a veterinarian by
noting the persistence of compatible clinical symptoms, after
ruling out other diseases which can cause similar symptoms.
If the allergy symptoms are mild and the pet responds well
to treatment for inhalant allergies, no further tests may
be needed. If the problem is more severe and does not respond
well to simple measures, then allergy testing should be considered.
The ideal method of testing for inhalant allergies or atopy
is Intradermal Skin Testing. This procedure is also the most
accurate method of identifying offending allergens for possible
avoidance or inclusion in an allergy desensitization treatment
program. Serum allergy testing is an easier option, but the
costs are not much different and we prefer the superior accuracy
of Intradermal Skin Testing.
Many veterinarians and veterinary allergy specialists have
achieved good Intradermal Skin Test results by taking advantage
of allergen cross reactivity and testing for reactions to
as few as 25-35 allergens. At the Chastain Veterinary Medical
Group we test for reactions to 52 of the most common allergens
in this area. This procedure takes longer, but for us, we
feel it provides a clearer picture of the pet’s true allergy
status.
- Flea allergies. This is a
common form of allergies among dogs and cats. Affected
pets typically scratch at the rump
or tail head area (dogs), or the head and neck area (cats),
leading to hair loss, scabs and open sores. Flea allergies
can be diagnosed by a veterinarian by noting the presence
of fleas or “flea dirt” in the coat, along with persistence
of compatible clinical symptoms after ruling out other diseases
which can cause similar symptoms. The diagnosis can be confirmed
by Intradermal Skin Testing, serum allergy testing, or by
observing the disappearance of symptoms once flea exposure
is eliminated.
- Food allergies. This is an
uncommon form of allergies among dogs and cats. Typical
offending food constituents are
proteins from chicken, milk, eggs, corn, wheat, soy, and
most especially, beef. Food allergic pets usually experience
a non-seasonal excessive scratching that responds poorly
to cortisone type medications. Food allergies can be diagnosed
by your veterinarian by noting the persistence of compatible
clinical symptoms after ruling out other diseases which
can cause similar symptoms. Confirmation of the diagnosis
requires demonstrating that symptoms resolve when the offending
foods are removed from the diet and reappear when the offending
foods are re-introduced.
- Bacterial Allergies. Bacterial
allergies appear to be a unique disorder of dogs. Cats
appear to be unaffected.
Bacterial allergies are an abnormal response to the presence
of normal skin bacteria of the genus Staphylococcus. Staph-allergic
dogs develop areas of hair loss and skin crusting that
look much like ringworm. Classically, the skin lesions
resolve when treated with antibiotics, only to recur when
the antibiotics are discontinued. This should be an important
clue to the veterinarian that there is more going on than
just a simple skin infection. Bacterial allergies can be
diagnosed by a veterinarian on the basis of patient history
and the recurrent symptoms, after ruling out other diseases
which can cause similar findings. The diagnosis should
ideally be confirmed by Intradermal Skin Testing.
- Contact allergies. Contact
allergy is the least common of the five types of allergy.
Contact allergies generally
produce localized skin reactions – redness, swelling, itching,
and hair loss. Examples of contact allergy include skin reactions
to flea collars, plastic pet food bowls, pet sweaters, or
wool bedding. Contact allergies can be diagnosed by your
veterinarian by noting the persistence of compatible clinical
symptoms after ruling out other diseases which can cause
similar symptoms. Confirmation of the diagnosis requires
demonstrating that symptoms resolve once the contact irritant
is removed, and re-appear when the pet is re-exposed to the
offending material.
Treatment
The protocols for treatment of Allergies in dogs and cats
vary somewhat with the type of allergy present. These are
discussed below.
- Inhalant allergies. Treatment
of inhalant allergies depends largely on how much the condition
is bothering the pet and
the pet owner. Treatment options for inhalant allergic pets
include the following:
- Avoidance /
Environmental Control – If the offending allergens are known, then
avoidance is the best method of treatment,
if feasible. Even if the pet is being desensitized with
allergy shots (see below), it still makes sense to avoid
the offending
allergens altogether, if possible. For example, indoor
mold allergies can be reduced by using a dehumidifier
or placing
activated charcoal on top of the exposed dirt in potted
house plants. Dusts and pollens are best controlled by
using an
air cleaner with a HEPA filter. Air conditioning can
also reduce circulating amounts of airborne allergens
because
windows are then kept closed.
- Topical Therapy - This
may involve nothing more than cool water baths with or
without colloidal oatmeal shampoos or
other medicated shampoos. This is easy, inexpensive and
can be repeated frequently, but it is labor intensive
and provides
only temporary relief.
- Dietary Supplementation - Omega-3 and Omega-6 Fatty Acids are natural anti-inflammatory
agents. Diets and dietary supplements
that contain both omega-3 and omega-6 fatty acids have
been shown to help reduce allergy symptoms. Examples
of omega
fatty acid supplements include Derm Caps™, and EFA-Z
Plus™.
- Diet Change - Certain
therapeutic pet foods, such as Eukanuba’s Response™ KO/Canine
Dry Formula and Response™ FP/Canine Dry
Formula are specifically formulated to soothe allergies
and contain both Omega-3 and Omega-6 fatty acids. These
food,
alone or in combination with addition fatty acid supplementation
from Derm Caps or EFA-Z Plus, have brought significant
relief to many pets.
- Antihistamines - Antihistamines
prescribed by a veterinarian are relatively safe and
effective in dogs and cats. Studies
indicate that ten to thirty percent of dog owners see
favorable results with antihistamines alone. They appear
to be even
more effective in cats. The major drawback to antihistamines,
as with people, is sedation. Antihistamines commonly
used in dogs and cats include: chlorpheniramine, diphenhydramine,
hydroxyzine, and clemastine.
- Corticosteroids - These
compounds reduce itching by reducing inflammation. Unfortunately,
they also affect every organ
in the body. They are perhaps best used when the allergy
season is short; the amount of drug required is small,
or
as a last resort to relieve a pet in extreme discomfort.
Side effects can include increased thirst and appetite,
increased need to urinate and behavioral changes. Long
term use has
been associated, in some cases, with diabetes, pancreatitis,
decreased resistance to infection and increased susceptibility
to seizures. Corticosteroids can be recognized by the
suffix "-one",
such as cortisone, dexamethasone, prednisone, etc.
- Immunotherapy
or “Allergy Shots” – The ideal method of treatment for inhalant allergies
or atopy is desensitization
of the patient with multiple antigen injections. These
are
often called "allergy shots".
Allergy shots are generally safe, effective, and many people
have had great success with them – either personally or in
their pets. The allergen mix in the allergy shots is customized
for each pet, based on the results of allergy testing; usually
intradermal skin testing. Once the specific allergens have
been identified, very small amounts of the offending antigen
are injected into the pet every 20-40 days or so in the Allergy
Shots.
The purpose of this therapy is to reprogram the pet's
immune system. It is hoped that as time passes, the immune
system will become less reactive to the problem-causing allergens.
If Allergy Shots appear to help the pet, injections will
need to continue for several years at a minimum. For most
pets, a realistic goal is for the itching to be significantly
reduced in severity; in a few lucky pets, the itching may
completely resolve.
The biggest drawbacks to immunotherapy
are that allergy testing is expensive (several hundred dollars),
allergy shots are very slow to work (months), and administering
the Allergy Shots is somewhat labor intensive. Still, the
success rate of immunotherapy based on allergy testing is
said to be about 60 – 80% - which is better than any other
form of allergy treatment.
- Flea allergies. The
most effective way to control flea allergies is to separate
the pet from the fleas. Therefore,
strict flea control is essential. This has been made
ever so much easier in the last few years, thanks to
the advent
of modern flea control products such as Frontline Top
Spot™, Revolution™, Advantage™, Advantix™, and Capstar™.
When strict flea control is not possible or practical, corticosteroids
can be administered, by injection or by pill, to block the
allergic reaction and give a pet some relief. This is often
a necessary part of dealing with flea allergies. As with
any effective and useful medication, there are side effects
to corticosteroid use. Fortunately, dogs and especially cats
are more resistant to the side-effects of steroids than humans;
so much of what you may have heard about the side-effects
of corticosteroids in people does not necessarily apply to
dogs and cats.
- Food allergies. Treatment
for food allergies involves avoidance of the offending
food ingredient(s). This is often
more difficult than it sounds. Generally, affected pets
will need to be switched to a pet food containing so-called
novel
proteins to which their immune system has not been exposed
before. We have seen good results after food allergic
pets have been switched to one of three special therapeutic
foods:
Purina HA™, Eukanuba Response™ KO/Canine Dry Formula,
or Eukanuba Response™ FP/Canine Dry Formula.
- Bacterial Allergies. Treatment
of Staph allergy involves antibiotics to control the
immediate problem and establishment
of a desensitization program, using killed Staph bacteria,
for long-term relief.
- Contact allergies. The
treatment of Contact Allergies is simple: just eliminate
exposure of the pet to the offending
substance(s). This can be accomplished as follows -
- Get
rid of irritating plastic food bowls, collars, or bedding.
- Bathe the pet with
hypoallergenic shampoos to remove antigen from the
skin.
- Create mechanical
barriers against further exposure, if possible. For
example, socks,
T-shirts, or fencing
to restrict
access to the irritating environment might
all prove helpful.
- Corticosteroids are
sometimes needed to help control symptoms.
Prevention
The only really effective long term solution to allergies
is to remove the offending substances from the pet’s environment
- or remove the pet from any possible exposure to those environmental
irritants. Sometimes this is easy to do, as in the case of
contact allergies, food allergies or flea allergies. Most
of the time, however, avoidance is not a realistic alternative.
Therefore, once a pet becomes symptomatic, some form of treatment
will usually need to be initiated and continued for the rest
of the pet’s life.
Remember, allergies are rarely cured.
The goal is
comfort and control.
An allergic pet that is comfortably
excessively
itchy is a success.
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