Allergies in Cats
What are
allergies?
The word allergy
means 'altered working'. Just like humans, cats can have
allergies too. Allergies are a common cause of skin disease in
cats.
The purpose
of the immune system is to keep infectious microorganisms, such
as certain bacteria, viruses, and fungi, out of the body, and to
destroy any infectious microorganisms that do invade the body.
Allergies are caused by an inappropriate response to a substance
which would usually be considered harmless.
In an allergic
animal, the immune system over reacts to the substance & mounts
an immune response against it.
Eosinophilic Granuloma Complex has
been linked to allergies.
What are the
causes of allergies?
There are four
causes of allergies in cats, insect, contact, inhalant & food.
Insect
Allergies:
Allergies to fleas
are the most common cause of insect
allergies in cats. There are 15 known allergens in flea
saliva, each one is capable of causing an allergic reaction in
the cat. Just one bite from a flea is enough to trigger an
allergic reaction in your cat. FAD is one of the major causes
of
miliary dermatitis
in cats. Symptoms of insect allergies
include; frequent scratching & biting of the fur, especially on
the back & the base of their tail. Other symptoms of flea
allergy dermatitis include raised bumps (papules) or scabs on
the skin & thinning fur in the affected area.
Symptoms of
insect allergies:
Some symptoms of
insect allergy include;
-
Itching &
scratching
-
Frequent
scratching & licking at the fur, especially over the base of
the tail & back of the thighs
-
Red, crusty
bumps, especially around the head, neck & back, often with
intense itching
Diagnosis of
insect allergy
-
This is
typically diagnosed by seeing the characteristic lesions on
the cat & ruling out other causes.
-
Biopsy of the
affected area.
-
Treating the cat
for fleas or keeping it indoor & therefore reducing it's
exposure to mosquitoes to see if the condition improves.
Treatment of
insect allergies would include;
-
Eliminating
fleas
from the cat & the environment.
-
Treating
secondary skin infections caused by excessive biting &
scratching of the skin. This may involve a course of
antibiotics, medicated shampoo & or a topical medication.
-
Antihistamines
or steroids may be prescribed by your veterinarian to control
inflammation & reduce itching.
-
Hyposensitisation (allergy shots/allergy
desensitization). This involves injecting gradually greater
amounts of flea antigen in the hope that it will re-programme
the immune system so it's not hypersensitive.
Food Allergies
This
is caused by an allergic reaction to one or more ingredients in
the cat's food. The most common causes of food allergies are
fish, beef, eggs, wheat & milk.
Symptoms of
food allergies:
-
Non seasonal
itching, especially on the front half of the body, head, face,
ears & neck.
-
The ears may
also be swollen & or infected
-
Hair loss (due
to excessive scratching, grooming etc)
-
Vomiting
& or
diarrhoea
Diagnosis of
food allergies:
Your veterinarian
will place your cat on a food trial which usually lasts between
8-12 weeks. During this time, you must not give your cat any
other foods, vitamins, minerals or chewable medications apart
from the prescribed diet. If any other foods or vitamins
are given during this trial it will invalidate the results. If
the allergy clears up after the specified time then a food
allergy is the likely cause. The diet given to your cat during
the trial is most often a food the cat has never had before such
as rabbit, duck or venison. The diet may be home made or a
special 'prescription' diet. This is known as 'elimination
food trial'. After the trial, if the cat's allergies have
cleared up it will be placed back onto it's regular food & if
after a short period of time the allergies return then it is
safe to conclude that the food was the cause of the allergy.
After the trial
you may be asked to 'challenge' your cat by re-introducing
one ingredient back into the diet. If after 2 weeks the
re-introduced food hasn't caused a flair up then add another
ingredient & so on. If the allergy returns with the
re-introduction of the ingredient then this is eliminated from
the diet once again.
Occasionally new
food allergies develop over time, if this happens then it will
be necessary to re-evaluate the new diet.
Treatment of
food allergies would include;
Avoiding the food
which caused the allergies is the best method of treatment. This
may either be a home made diet or a commercial one. If you are
feeding a home made diet it is important to ensure that your cat
is receiving the correct nutrients in the diet.
Inhalant (atopy)
Allergy
This is an
allergic reaction caused by breathing pollens, dust, moulds &
other allergens in the environment. It is under diagnosed in
cats [1]
Symptoms of
inhalant allergy:
Symptoms can be
seasonal or non seasonal & often begin in young cats, worsening
with age.
Diagnosis of
inhalant allergy:
Your veterinarian
will obtain a complete medical history from you & perform a
physical examination. He will want to rule out other possible
conditions such as mange, flea allergy, contact dermatitis,
ringworm & food allergy.
-
Skin scrapings &
fungal cultures to rule out some of the conditions above.
-
Intradermal skin
test: A small amount of allergen is injected through the skin,
which is then observed to determine if elicit an allergic
reaction. Certain medications such as antihistamines may
interfere with results.
-
Blood test: This
tests for antibodies to specific antigens in the blood. There
are two tests used in cats, radioallergosorbent test (RAST)
and enzyme-linked immunosorbent assay (ELISA). [2]
Treatment of
inhalant allergy:
Treatment may
include;
-
Avoiding the
cause of the allergy if possible is the ideal method to treat
inhalant allergy but is often not possible because of an
inability to identify the allergen or halt exposure.
-
Hyposensitisation (allergy shots/allergy desensitization).
This involves injecting gradually greater amounts of the
allergen in question in the hope that it will re-programme the
immune system so it's not hypersensitive to the antigen.
-
Corticosteroids
are beneficial in relieving symptoms but are not a cure.
-
Essential fatty
acid supplements have also been effective in some cases of
inhalant allergy.
Contact Allergy
This is the least
common of the four types of allergy in cats. Contact dermatitis
is a result of the cat coming into contact with a substance. The
cat's fur acts as a barrier, protecting it from allergy
producing compounds.
There are two
causes of contact dermatitis; allergic & irritant.
Irritant Contact
Dermatitis:
Irritant
dermatitis, the most common type of contact dermatitis, involves
inflammation resulting from contact with acids, alkaline
materials such as soaps and detergents, medications, solvents,
or other chemicals.
Allergic Contact
Dermatitis:
The second most
common type of contact dermatitis is caused by exposure to a
material to which the person has become hypersensitive or
allergic.
It arises some
hours after contact with the responsible material, and settles
down over some days providing the skin is no longer in contact
with it. Plants, wool, medications are a common cause of
allergic dermatitis in cats.
Symptoms of
contact allergy:
-
Non seasonal
itching, especially in areas where there isn't much fur.
Typical areas include the chin, ears, toes, underbelly & anus.
-
Lesions of any
type: redness, rash, papules (pimple-like), vesicles, and
blisters
-
Skin redness or
inflammation
-
Thickening of
the skin
Diagnosis of
contact allergy:
Your vet will
perform a physical examination & take a history. He/she will
want to rule out other causes of dermatitis (such as flea bite
hypersensitivity) first.
-
A skin biopsy
may be performed.
-
A patch test may
be performed. This involves applying various substances to
the skin, which is then bandaged over. This is then examined
at 24 & 48 hours. A positive reaction will be seen as redness
& swelling at a specific site.
-
A presumptive
diagnosis may be made by removing your cat from the
environment for a week , if lesions begin to heal, then recur
once returned to the environment.
Treatment of
contact allergy:
-
Identification &
elimination of the substance causing contact allergy is the
best solution.
-
Corticosteroids
may be prescribed to relieve pruritus.
-
Antibiotics may
be necessary to treat secondary bacterial infections.
References:
[1] Cat Health
Encyclopedia - Lowell Ackerman (p 14)
[2] The Feline
Patient -Gary D. Norsworthy, Mitchell A. Crystal, Sharon K.
Fooshee, Larry P. Tilley (p 122)
Please note:
The medical
articles on this site have not been written by a
veterinarian & should not be considered a replacement for a
veterinarian visit. The articles are provided for
informative purposes only.
Always seek
immediate veterinary advice for any problems (health or
behavioral) in your pets.
While great
care has been made in the creation of these articles, we
cannot guarantee the accuracy or omissions on these pages.
If in any doubt whatsoever, seek professional medical
advice.
