Third Street
Veterinary Hospital, PC
McMinnville, Oregon 97128
Office phone: (503) 472-9418
Allergies in
Cats
Overview
One
of the most common conditions affecting cats is 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.
Types of Allergy
There
are four known types of allergies in the cat: contact, flea, food, and
inhalant. 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 to 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 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 will often 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 out every 14-21 days. When strict flea control is not possible,
injections of corticosteroids (or "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
appear relatively more resistant to the side effects of steroids than other
species. If a secondary bacterial
infection occurs, appropriate antibiotics must be used.
Inhalant
Allergy
The
most common type of allergy is the inhalant type, or atopy. Cats may be allergic to all of the same
inhaled allergens that affect us. These
include tree pollens (cedar, ash, oak, etc.), grass pollens (especially
Bermuda), weed pollens (ragweed, etc.), molds, mildew, and the house dust
mite. Many of these allergies occur
seasonally, such as 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.
In fact, the most common cause of itching in the cat is inhalant
allergy.
Most
cats that have an inhalant allergy are allergic 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 they 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. If steroids are appropriate for your cat, you will be instructed
in their proper use.
Some
cats are helped considerably by a hypoallergenic shampoo. 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 allergy are identified, very small amounts
of the antigen are injected weekly.
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. Steroids are not used with this treatment
protocol, except on an intermittent basis.
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 used 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.
1. Cost: This is the most expensive form of
treatment.
2. Age of Patient: Because many cats develop
additional allergies as they get older, young cats may need to be re-tested 1-3
years later.
3. 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 undergoing desensitization.
4. 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.
5. Time of Response: The time until apparent
response may be 2-5 months, or longer.
6. Interference of steroids: Cats must not
receive oral steroids for 2 weeks or injectable steroids for 6 weeks prior to
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, these must be discontinued during the
testing period.
Because
cats that are being tested for inhalant allergy generally itch year round, a
food allergy dietary test can be performed while the inhalant test and antigen
preparation are occurring.
INSTRUCTIONS: Those instructions that are specific for
your cat have been checked:
___
1) An injection of steroids was
given. Relief should be apparent within
12-24 hours. If not, please call. The cat should feel better and itch less for
about one month. If an increase in water
consumption or urination occurs, please report this to us for future
reference. These side effects are
common with steroid administration and will go away in a few days without
treatment. Return for further
evaluation when the first signs of itching recur.
___
2) Begin oral steroids when the first
signs of itching return. Give ____
tablets every other evening. Adjust
dosage upward or downward to the lowest effective dose, with a maximum dose of
__________ permitted. Stop giving the
medication every 4-6 months to see if there are times of the year when therapy
is not needed. Report any increase in
water consumption to us at once.
___
3) We have dispensed oral steroid
tablets. Prednisone is most commonly
used. The specific drug being dispensed
for your cat is labeled on the bottle.
Give ____ of the ____ mg tablets every other day for 3 doses (6 days),
then ____ tablets every other day for 3 more doses (6 more days). Continue this downward progression
(___________________________________) until the first signs of itching
recur. At that time, go back to the
next higher level and report that level to us (so we can be sure it is a safe
level). Stop giving the tablets every
4-6 months to see if there are periods of the year when they are not necessary. When itching returns, begin immediately at
the maintenance dose. If that does not
stop the itching, increase the dosage slightly (to a maximum of ___ tablets)
for a few doses, then return to the lower dose. Report any increase in water consumption to us at once. (This may occur at the initial dose but
should stop on the maintenance dose.)
___
4) Your cat is to exclusively eat a hypoallergenic diet. If it will not do so readily, mix it 25:75
with the current diet for several days, then gradually increase the special
diet to 100%. If this does not work,
contact us for an alternative plan.
Discontinue any chewable treats or vitamins. Table food is not allowed.
Offer only distilled water to drink, if that is possible.
___
5) Your cat has a flea allergy or has
enough fleas to make the other allergy problem worse. Flea control is very important and should include treating the
cat and its environment. Bear in mind that
flea allergies often accompany other types of allergies, especially inhalant
allergy.
___
6) Your cat has a bacterial skin
infection secondary to allergy.
The
following are recommended:
a)
Antibiotics are to be used for the next _____ days. If the infection is not gone by the time the medication is
completed, call for a refill or for a change in medication.
b)
The medicated shampoo, _____________________, is to be used every _____
days. Allow the shampoo to stay in the
hair coat for a few minutes before thoroughly rinsing the cat.
c)
The topical medication, _____________________, is to be used ______ times daily
for __________ days.