Atopy - An Allergic Skin Reaction
Everyone
wants his pet to look healthier and feel good. But if he’s suffering from some
sort of allergic skin reaction – atopy, the itching can put your dog or cat
into distress, and the clinical signs involving redness, rashes, bleeding, and
skin infections are worse. They may occur by environmental allergies, which
typically can be cured with a range of things, from removing known allergens
from the environment to antihistamines and supplements to immunotherapy or
immunosuppression, depending on the allergic reaction and the pet.
 |
| Atopy - An Allergic Skin Reaction |
Introduction
Atopy
(also termed as “atopic dermatitis” and previously known as “allergic inhalant
dermatitis”) is a common dog and cat condition in which allergens present in
the environment cause an allergic reaction in the skin. It is one of several
known causes of allergic skin disease, a common umbrella term for a group of
allergies that are visible in the skin.
Atopy
is believed to occur when certain proteins present in the environment are taken
into the body through inhalation or direct contact with the skin. When they
precipitate an allergic response, these proteins are referred to as allergens.
When the allergic response occurs in the skin, the result is always an
inflammation of the skin we refer to as “allergic dermatitis.”
Common
allergens include pollen (from grasses, trees, and weeds), mold spores, house
dust/house dust mite proteins, insect proteins, and other miscellaneous
proteins that may also come from human skin or natural fibers, for example.
Atopic animals will display individual responses to one or more environmental
allergens.
Atopic
dermatitis in dogs has genetic basis, but this has not been proven in cats. In
both species, other factors including geography (regional pollens and plants),
the presence of other allergens (like fleas) and endocrine diseases (like
thyroid disease in dogs) — can worsen atopic disease.
Animals
with atopy become very itchy; the resultant scratching leads to skin injuries
and secondary skin infections. Atopy is usually first noticed in dogs and cats
younger than 3 years of age, although older pets can also be affected.
Unfortunately, pets that develop atopy are usually plagued by skin problems
throughout their lives.
Clinical
Signs
Atopic
dermatitis is characterized by the variable presence of itching, redness,
pustules (infected pimples), wheals (like hives), and crusts. The face, legs,
feet, ventrum (belly, underarms, and groin), and ears are most commonly
affected, but no area of the body is off the radar. In dogs, ear infections are
commonly associated with atopy.
Cats
usually exhibit signs of excessive licking in a symmetrical pattern (on the
belly, back, and behind the legs is most common) and/or they can develop tiny
scabs around the neck, tail base, or elsewhere on the body.
A more comprehensive list of signs in dogs and cats includes:
- Generalized scratching and rubbing
- Redness of the skin
- Hair loss from repeated biting, licking, chewing, and/or scratching
- Skin rash, infections, and irritation
- Scabs and bleeding
- Unusual odor
- Skin thickening and color changes
- Ear infections
- Scales and crusts on the skin
A
hallmark of atopic dermatitis is that signs tend to be seasonal and tend to wax
and wane in severity. However, pets that are allergic to house dust mites or
other indoor allergens can have year-round problems, because exposure to indoor
allergens is not dependent on season of the year.
Most
pets are diagnosed based on signs, history, and response to treatments, but
getting to a definitive diagnosis can be a difficult job. Given that every
affected animal suffers a highly individualized version of the disease,
determining what an animal is allergic to may require intradermal (skin)
testing and/or serum testing (blood testing).
Intradermal
skin testing can sometimes be performed at a vet lab. However, the allergens
used for this test are very specific (they vary depending on your region of the
country), your veterinarian may refer you to a veterinary dermatologist.
Usually,
an area of fur is shaved from your pet to expose enough skin to perform the
test. Tiny amounts of each test allergen are injected using very small needles
just under your pet’s skin in different areas. After a brief waiting period,
your veterinarian will examine the injection sites to measure the degree of
local allergic response (redness or a small hive). Allergens that your pet is
not allergic to will not cause a reaction, and allergens that your pet is
allergic to will cause a reaction that corresponds to the severity of the
allergy. Pets are monitored carefully during the procedure in case a serious reaction
occurs and treatment is required.
The
other type of allergy testing is serum allergy testing which is becoming more
popular. The test is performed at a laboratory using a small blood sample taken
from your pet so that your veterinarian does not need to shave your pet or have
special allergens on hand. As with intradermal skin testing, the results of
serum allergy testing can reveal which allergens are not causing an allergic
reaction in your pet, which ones are causing a mild reaction, and which ones
are causing a more serious reaction.
Depending
on which type of allergy test is performed, you may need to discontinue your
pet’s allergy medications before the test. Otherwise, the test results may be
affected. Your veterinarian will tell you which medications can be used and
which ones may need to be discontinued.
Affected
Breeds
Any
breed of cat or dog may be affected by atopy, but in dogs it is most prevalent
among Boston Terriers, Boxers, most Bulldog breeds (particularly English
Bulldogs), Cairn Terriers, Shar-peis, Dalmatians, English Setters, Golden
Retrievers, Irish setters, Labrador Retrievers, Lhasa Apsos, Miniature Poodles,
Miniature Schnauzers, Pugs, Scottish Terriers, West Highland White Terriers,
and Wire-Haired Fox Terriers.
Treatment
Four
categories of treatment have been described. They comprise:
1. Avoidance/ Cause removal (removing allergens from the environment or changing environments altogether)
This
is typically undertaken only after a list of allergens is identified via blood
or intradermal testing.
2.
Symptomatic therapy (as when using antihistamines, fatty acid supplements,
medicated shampoos, and antimicrobials for common secondary bacterial and yeast
infections) is the most common approach to treatment, especially for pets with
mild clinical signs.
Antihistamines:
Drugs like diphenhydramine have few side effects compared with some other
therapies. However, some pets will not respond to antihistamines alone. Avoid
giving human drugs to your pet unless directed to do so by your veterinarian.
Fatty
acid supplements: Special fatty acid supplements may help reduce skin
inflammation and are often used in combination with other medications.
Topical
treatments: Medicated shampoos, leave-on conditioners, and ointments can
relieve a pet’s itching or help with secondary conditions such as fungal
infections, bacterial infections, and scaling. Treatment should be repeated
frequently for best results, but be sure to follow all label directions
carefully. Avoid the use of human products on pets unless they are recommended
by your veterinarian.
3.
Immunotherapy (using specific allergens to desensitize a pet to the proteins)
Once
a list of “problem” allergens is identified via blood or intradermal skin
testing, a specialized “serum” containing small quantities of these allergens
can be formulated specifically for your pet. Through injection of small amounts
of the allergy serum over time, many pets experience a reduced response to the
allergens.
This
treatment, called immunotherapy, generally must be continued for several months
to years to achieve results. With immunotherapy, the pet owner generally
administers the allergy serum injections at home. If you are uncomfortable with
giving injections, ask your veterinary care team if the injections can be given
at your veterinarian’s office. The first injections are more diluted, and each
following injection has a slightly higher concentration of the allergens. Your
veterinarian will schedule the injections according to specific guidelines —
more frequently in the beginning, and eventually tapering to one injection
every few weeks. Many pets respond to this program. Others may not, especially
if they have other underlying conditions.
4.
Immunosuppressive therapy (with corticosteroids like prednisone, cyclosporine,
or other drugs)
Unfortunately,
some pets’ atopic disease cannot be controlled by any of the above approaches
and their quality of life may suffer drastically unless more intensive drug
therapy is initiated:
Steroids:
Drugs like prednisone or dexamethasone, which are called corticosteroids, are
often used because they tend to be very effective and safe for short-term use.
These medications can be given by injection, by mouth, or as topical ointments
or shampoos. Corticosteroids can provide immediate relief but may have
undesirable side effects, such as increased appetite, thirst, and urination. In
some cases, repeated or long-term use of steroids can be associated with an
increased risk of medical problems such as liver problems, adrenal gland
problems, and diabetes.
Cyclosporine:
Cyclosporine can be used to control atopic dermatitis in dogs and allergic
dermatitis (including atopy) in cats. The medicine is given once a day for 4
weeks (4 to 6 weeks in cats, based on response). After that, the dose can be
tapered to every other day or twice weekly, as needed to maintain
effectiveness. Researchers estimate that over 70% of dogs and cats respond to
this treatment; however, cyclosporine can be costly, and its side effects may
include stomach upset and diarrhea. Ask your veterinarian if cyclosporine may
be a good choice for your pet.
Prevention
Many
of the therapies described here can be used to control atopy over the long
term. Avoidance of problem allergens may be the best way to prevent flare-ups
for dogs and cats with atopy.
This
article has been peer reviewed for accuracy by a Veterinarian.