Canine Atopic Dermatitis

Atopic dermatitis (allergic dermatitis, inhalant dermatitis,
atopy) is an inherited predisposition to develop allergic
symptoms after repeated exposure to some otherwise harmless
substance, and “allergen” such as dust, dust mites, grasses, or
pollen. Most dogs begin to show their allergic signs between 1
and 3 years of age. A few dogs may show clinical symptoms at 6
months of age. It is also unusual to see clinical symptoms start
after 7 years of age.

Because of the hereditary nature of the disease, several breeds,
including golden retrievers, most terriers, Irish and English
setters, Lhasa apsos, dalmatians, bulldogs, beagles, miniature
schnauzers and Chinese Shar Peis, are more commonly “atopic.”

Atopic animals usually rub, lick, chew, bite, or scratch at
their feet, muzzle, ears, armpits, or groin, causing hair loss
and reddening and thickening of the skin. In some cases, several
offending substances can “add” together to cause an animal to
itch where each individual substance alone would not be enough
to cause an itching sensation.

These substances include not only airborne allergens (e.g.,
pollens) but also allergens in food and allergens from parasites
(e.g., fleas) and itching caused by bacterial or yeast
infections of the skin. Sometimes, eliminating some but not all
of the problems may cause a dog’s or cat’s itchiness to go away.
Therefore, it is important to treat any other problems that
could be making your pet itch while dealing with allergy.

Diagnosis of atopic dermatitis is based on clinical sighs (areas
of itching) and an initial seasonality of the skin problem.
However, many dogs soon begin to scratch and rub year round.
Specific therapy is based on the results of a skin test or blood
test to detect reaction to the specific allergic substance.

Treatment can include avoidance of the substance, therapy to
control the itching (symptomatic therapy), or specific therapy
(desensitization vaccine) in an attempt to desensitize your pet
to the specific substances to which he or she is found to be
allergic.

Complete avoidance of the allergic substance may not be
practical, but decreased exposure may be feasible. If your pet
is allergic to pollen, decreasing the outdoor exposure
especially at dusk and dawn is helpful. Your pet should never be
walked through fields with high grass or weeds and should not be
outside when the lawn is cut.

If your pet has an allergy to fungi or molds, it should not be
keep in rooms with high moisture levels (bathroom or laundry
room) or allowed to be in areas of increased dust (crawl spaces
under the house). Control of house dust or mites in the home can
be a major undertaking, consisting of removing carpeting,
covering mattresses, regular washing of the bedding,
high-efficiency vacuuming, avoiding stuffed toys, and frequent
damp mopping of the areas most frequented by your pet.

Antihistamines and fatty acids, when given in combination, can
decrease the itching sensation in about 10 to 20 per cent of
atopic pets. Your pet can take antihistamines and fatty acids
for life with no long-term problems. The only side effect
usually seen with antihistamines is drowsiness. Several
different types of antihistamines may need to be tried to find
the one that works the best. These two combined therapies
(antihistamines together with fatty acids) should be given a few
months before a decision is made concerning their effectiveness.

Products applied topically to the skin (shampoos, cream rinses,
leave-on conditioners, gels, lotions, sprays) with anti-itch
properties may also be of benefit. These products usually need
to be applied daily (sprays, gels, lotions) or a few times
weekly (shampoos, cream rinses, leave-on conditioners). It is
most important that your pet be bathed in cool water because
warm or hot water increases the itching sensation.

Steroids (e.g., prednisone, cortisone) can be formulated for
your pet on the basis of results of a skin test or blood test.
These vaccines are usually given for the lifetime of your pet.
After an initial series of injections, periodic boosters are
needed (every few weeks). Sixty to 80 per cent of animals
improve with these vaccines. However, desensitization takes
time. Improvement may not be seen for 3 to 6 months or longer.
If results are not seen in 9 to 12 months, a reevaluation of the
vaccine usage is necessary.

Allergies are a lifelong problem and tend not to just go away.
The best chance for success is realized when you can spend the
time and effort in utilizing symptomatic therapy only on your
pet or while your pet is undergoing the process of
desensitization. Only by trial and error can the optimal therapy
be formulated. Time and patience are the keys!

The above is general veterinary information. Do not begin
any course of treatment without consulting your regular
veterinarian. All animals should be examined at least once every
12 months.