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What are allergies, and how do they affect cats?
One of the most common conditions affecting cats is an
allergy. In the allergic state, the cat's immune system "overreacts" to
foreign substances (allergens or antigens) to which it is exposed. Those
overreactions are manifested in three ways. The most common is itching of
the skin, either localized (one area) or generalized (all over the cat).
Another manifestation involves the respiratory system and may result in
coughing, sneezing, and/or wheezing. Sometimes, there may be an associated
nasal or ocular (eye) discharge. The third manifestation involves the
digestive system, resulting in vomiting or diarrhea.
Are there several types of allergies?
There are four known types of allergies in the cat:
contact, flea, inhalant, and food. Each of these has some common expressions
in cats, and each has some unique features.
Contact Allergy
Contact allergies are the least common of the four types of
allergies. They result in a local reaction on the skin. Examples of contact
allergy include reactions to flea collars or to types of bedding, such as
wool. If the cat is allergic to those, there will be skin irritation and
itching at the points of contact. Removal of the contact irritant solves the
problem. However, identifying the allergen can require some detective work.
Flea Allergy
Flea allergy is very common in cats. A normal cat
experiences only minor irritation in response to flea bites, often without
any itching. The flea-allergic cat, on the other hand, has a severe,
itch-producing reaction when the flea's saliva is deposited in the skin.
Just one bite causes such intense itching that the cat may severely scratch
or chew itself, leading to the removal of large amounts of hair. There may
be open sores or scabs on the skin, allowing a secondary bacterial infection
to begin. The area most commonly involved is over the rump (just in front of
the tail). In addition, the cat may have numerous, small scabs around the
head and neck. These scabs are called miliary lesions, a term which was
coined because the scabs look like millet seeds.
The most important treatment for flea allergy is to get the
cat away from all fleas. Therefore, strict flea control is the backbone of
successful treatment. Unfortunately, this is not always possible in warm and
humid climates, where a new population of fleas can hatch every 14-21
days.
There are some new, effective products that can be a
valuable part of the overall treatment plan:
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Spot treatment — Frontline, Advantage, or
Revolution/Stronghold (Revolution works extremely well, but it's expensive).
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Tablets — Program is helpful in flea control, but it does
not prevent your cat from picking up new fleas.
CAUTION:
Whatever product you use, be sure to follow all label instructions very
carefully. Cats, and particularly kittens, are extremely sensitive to
insecticides and can die from inappropriate use of these products. What is
safe for an adult cat may not be safe for kittens. For kittens: The label
must clearly state that the product is safe for kittens and at what age. If
the product is safe only for kittens 6 weeks of age and older, it must not
be used when the kitten is 5 weeks old. Never use dog products on a cat
unless the label specifically states that it can be used on a cat.
It is important to treat your house for fleas, not only
your cats.
When strict flea control is not possible, injections of
corticosteroids (cortisone, or steroids) can be used to block the
allergic reaction and give relief. This is often a necessary part of dealing
with flea allergies. Fortunately, cats are more resistant to the
side-effects of steroids than other species. If a secondary bacterial
infection occurs, appropriate antibiotics should be used.
Inhalant Allergy
A common type of allergy is the inhalant type, or atopy.
Cats may be allergic to all of the same inhaled allergens that affect people.
These include tree pollens (cedar, ash, oak, and so on), grass pollens
(especially Bermuda), weed pollens (ragweed, and so on), molds (including leaf
molds), mildew, and the house dust mite.
Many of these allergies occur seasonally, such as to
ragweed, cedar, and grass pollens. However, others are with us all the time,
such as molds, mildew, and house dust mites. When humans inhale these
allergens, we express the allergy as a respiratory problem; it is sometimes
called "hay fever." The cat's reaction, however, usually produces severe,
generalized itching. The most common cause of itching in the cat may be
inhalant allergy.
Most cats that have inhalant allergy react to several
allergens. If the number is small and they are the seasonal type, itching
may last for just a few weeks at a time during one or two periods of the
year. If the number of allergens is large or they are those that are present
year-round, the cat may itch constantly.
Treatment depends largely on the length of the cat's
allergy season. It involves two approaches. Steroids will dramatically block
the allergic reaction in most cases. These may be given orally or by
injection, depending on the circumstances. As stated previously, the side
effects of steroids are much less common in cats than in people. Usually the
only side effect in cats is an increase in appetite. If steroids are
appropriate for your cat, you will be instructed in their proper use.
Some cats are helped considerably by a hypoallergenic
shampoo if the cat will tolerate baths. It has been demonstrated that some
allergens may be absorbed through the skin. Frequent bathing is thought to
reduce the amount of antigen exposure through this route. In addition to
removing surface antigen, bathing alone will provide some temporary relief
from itching and may allow the use of a lower dose of steroids.
Antihistamines are usually of little value in the cat but can be tried.
The second major form of allergy treatment is
desensitization with specific antigen injections (or "allergy shots"). Once
the specific sources of the allergy are identified, very small amounts of
the antigen are injected weekly by the guardian. This is all in an attempt to
reprogram the body's immune system. It is hoped that as time passes, the
immune system will become less reactive to the problem-causing allergens. If
desensitization appears to help the cat, injections will continue for
several years.
For most cats, a realistic goal is for the itching to be
significantly reduced in severity; in some cats, itching may completely
resolve. Generally, steroids are not used with this treatment protocol. This
therapeutic approach is recommended for the middle-aged or older cat that
has year-round itching caused by inhalant allergy. This approach is not
successful with food allergy.
Although desensitization is the ideal way to treat inhalant
allergy, it does have some drawbacks and may not be the best choice in
certain circumstances and for these reasons:
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Cost: This is the most expensive form of treatment.
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Age of Patient: Because many cats develop additional
allergies as they get older, young cats may need to be retested 1-3
years later.
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Success Rate: About 50% of cats will have an excellent
response. About 25% get partial to good response. About 25% get little
or no response. The same statistics are true for people.
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Food Allergies: Although "tests" for food allergy are
available, the reliability of the test is so low that it is not
recommended at this time. A food trial remains the best diagnostic test
for food allergy.
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Time of Response: The time until apparent response may
be 2-5 months, or longer.
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Interference from steroids: Cats must not receive oral
steroids for 2 weeks or injectable steroids for 6 weeks before
testing; these drugs will interfere with the test results.
Food Allergy
Cats are not likely to be born with food allergies. More
commonly, they develop allergies to food products they have eaten for a long
time. The allergy most frequently develops in response to the protein
component of the food; for example, beef, pork, chicken, or turkey.
Food allergy may produce any of the clinical signs
previously discussed, including itching, digestive disorders, and
respiratory distress. We recommend testing for food allergy when the
clinical signs have been present for several months, when the cat has a poor
response to steroids, or when a very young cat itches without other apparent
causes of allergy.
Testing is done with a special hypoallergenic diet. Because
it takes at least 8 weeks for all other food products to get out of the
system, the cat must eat the special diet exclusively for 8-12 weeks (or
more). If positive response occurs, you will be instructed on how to
proceed. If the diet is not fed exclusively, it will not be a meaningful
test. We cannot overemphasize this. If any type of table food, treats, or
vitamins are given, they must be discontinued during the testing period.
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