Is Your Pet Itching for Relief?
My-Dog.info > Dog Health
When your dog pumps its leg frantically to scratch its ear, or
your cat bites its tail furiously until the fur falls out, it's
clear that your pet is itching for relief.
Occasional scratching is normal, but if a pet scratches or
bites itself relentlessly, a health problem may be the cause.
Itching can be triggered by a variety of conditions, ranging from
liver disease to lice, from fungus to fleas, from mange to
anxiety.
But the leading cause of itching and scratching in pets is
allergies, says Linda Messinger, D.V.M., a board-certified
veterinary dermatologist at the Veterinary Referral Center of
Colorado in Englewood. "Allergies are also the most common
underlying cause of ear problems in dogs," she adds.
Unlike people with allergies, animals don't usually get stuffy
or runny noses or watery eyes. Their main symptom is itchy skin,
which can turn raw and red from scratching, licking, and chewing.
This condition is called allergic skin disease, or allergic
dermatitis. With enough scratching and biting, open sores can
form, creating a haven for bacteria or yeast that can lead to
infection.
"Just about every mammal can get allergies," says
Lisa Troutman, D.V.M., a veterinarian with the Food and Drug
Administration. "So can hamsters, rabbits, birds, and some
other pets." But dogs and cats are the pets most frequently
seen with allergies.
To relieve the itch, dogs may scratch and bite at themselves
and rub their face with their paws or against the floor and
furniture. "Cats tend to pull out their hair and get patchy
hair loss on their ears, legs, and around their eyes," says
Troutman. "They'll make themselves bald."
There is no cure for allergies. "They are a lifelong
problem," says Messinger, "and oftentimes they get
worse as a pet gets older."
But there are treatments to relieve itchiness, clear up
infections that arise from constant scratching, and even
"desensitize" a pet to substances that cause allergies.
In addition to regulating drugs for people, the FDA regulates
drugs for animals, and the agency's Center for Veterinary
Medicine has approved medications to treat itchy pets and their
infections.
The key to making your pet comfortable is to find out the
cause of the itchiness. If the pet is allergic, determining the
source of the allergies will help with treatment, says Messinger.
Types of Allergies
Allergies that can plague pets are grouped into four types:
flea, food, atopic, and contact.
The most common type of allergy in both dogs and cats is flea
allergy. The offending allergen is actually the protein in flea
saliva left in the skin after a fleabite.
Atopic, or inhalant, allergy is the second most common allergy
in dogs and the third most common in cats. Breathing in or
directly contacting airborne particles in the environment, such
as mold spores, dust, tobacco smoke, and pollens, will activate
atopic allergies.
If a pet is allergic to pollens, it will show symptoms even if
you keep it indoors, says James Jeffers, V.M.D., a
board-certified veterinary dermatologist at the Animal Allergy
and Dermatology Clinic in Gaithersburg, Md. Outside airborne
substances waft their way into the house, and air filters don't
tend to bring relief to pets with these types of allergies, he
says.
Although pets with atopic allergies sometimes have respiratory
problems, such as coughing and sneezing, they more typically
develop itchy skin. Certain dog breeds are more likely to develop
atopic allergies, including terriers, Dalmatians, and golden and
Labrador retrievers.
Food allergies are the second most common type of allergy in
cats and the third most common in dogs. Food ingredients most
likely to trigger allergies in cats are fish, milk, beef, and
eggs. Ingredients most likely to cause a reaction in dogs are
beef, soy, chicken, milk, corn, wheat, and eggs. Some pets with
food allergies may have vomiting and diarrhea.
A reaction to physically touching a substance is called
contact allergy, the least common type of allergy in dogs and
cats. Contact allergens include grass, wool, and plastic. Jeffers
occasionally sees dogs in his clinic with "plastic dish
dermatitis," an irritation to the skin on the nose caused by
a reaction to an antioxidant found in a plastic food or water
dish. The condition clears up when the pet is switched to a metal
or ceramic dish. And although uncommon, some cats become allergic
to kitty litter, says Jeffers. But allergies caused by contact
with chemicals, such as those contained in cleaning fluids,
waxes, carpet cleaners, and lawn fertilizers, are "about 1
in a million," he says. Nevertheless, these products are
potentially toxic, and pets should be restricted temporarily from
areas treated with them.
An Itch for All Seasons
Some pets' allergies are set off by seasonal changes.
Springtime, with its tree pollens, brings on the animal form of
hay fever, which is primarily itchy skin. Mosquitoes and flies,
which may trigger allergies, are rampant in summer. Grasses and
flowers often release pollen in summer and late-blooming plants
produce pollen in early fall, creating airborne irritants. Fleas
and the allergies they activate persist in spring through fall in
most parts of the country, but are found year-round in some
areas.
Geography also plays a role in allergic reactions. Regional
changes mean different varieties of grasses, trees, insects, and
other environmental elements, which can affect allergies. Jeffers
says when he took his dog camping in Maine, the pup was healthy,
but when he brought him back home to Maryland, he started
itching.
The Allergic Reaction
Pets, like people, have allergic responses when their immune
system overreacts to certain substances. When they enter the
body, the offending substances, called antigens or allergens, set
off an alarm. This alarm stimulates the body to produce
antibodies to defend itself against what it perceives as a
threat--the allergen invaders. The antibodies attach themselves
to immune cells, called "mast cells," within the skin
and other body tissues. When the allergens penetrate these
tissues' surfaces, they are captured by the antibodies, which
then stimulate the mast cells to release powerful chemicals into
the surrounding tissues. It is these chemicals, called
histamines, that cause inflammation and itching.
The body's immune system is meant to protect against harmful
substances, so why do some animals have a severe reaction to
non-threatening substances? "We think it's very similar to
the situation in human beings," says Daniel O. Morris,
D.V.M., a board-certified veterinary dermatologist and chief of
staff of the veterinary hospital at the University of
Pennsylvania in Philadelphia. Some animals, like some
individuals, "may carry genes that put them at risk for
developing allergic reactions," he says.
Another explanation is the hygiene theory, says Morris, which
suggests that if you allow children to be exposed to infectious
organisms early in life, their immune response may better control
infections and make them less likely to develop allergies. In
societies that stress cleanliness and try to protect children
from dirt and disease, a child's body may overreact when
confronted with a foreign substance, even a harmless one. The
hygiene theory may explain why allergies in children are on the
rise in the developed world, and the same explanation could apply
to allergies in pets, says Morris.
Diagnosing
There are many conditions that can make a pet itch or have
hair loss, including endocrine, autoimmune, infectious, and
parasitic skin diseases. It takes some detective work to identify
the cause. A veterinarian may be able to diagnose the problem or
may refer your pet to a veterinary dermatologist, a specialist in
treating skin conditions in animals.
If allergies are suspected, the first thing a veterinarian
will usually ask is if the pet is on a flea-control product, says
Troutman. Flea allergies are the most common type of allergies
and the easiest to control, she says. And just because a pet is
kept indoors doesn't mean it can't have fleas. An owner might
bring fleas into the house on a piece of clothing, and the fleas
can jump onto the pet. Just a single fleabite can cause an
allergic animal to itch severely for more than five days,
according to the American Animal Hospital Association.
Pet owners have many options for flea control on pets and in
their environment. Veterinarians can recommend an appropriate
product.
Once flea allergies are ruled out and if the itch is
non-seasonal, food allergies are checked next. Food allergies are
not related to a season, while many atopic allergies start out as
a seasonal problem, says Morris. Dogs and cats that develop
atopic allergies usually show symptoms between 1 and 5 years of
age, he says, but food allergies can crop up at any time. They
are high on the list of suspects when a dog or cat first exhibits
itchy skin at an age less than 6 months or over 5 years.
To test for food allergies, the pet is put on an
"elimination diet" for at least 10 weeks, which means
it is fed food that consists of a protein and carbohydrate that
the pet has not eaten before, such as duck, venison, and
potatoes. Veterinarians offer these special foods, and some may
be found in retail stores. Or the owner may choose to feed the
pet a homemade diet of foods recommended by the vet.
If the animal's itching subsides by at least half, the
allergen is considered to be one or more food ingredients, says
Jeffers. To confirm this, the owner can reintroduce the old food
to see if the symptoms return. To find the specific ingredients
that trigger the allergy, the owner should feed the special diet
again and add one ingredient at a time from the old diet for at
least a week until the itching increases, indicating that the
last added ingredient is an allergen. Or the owner may choose to
stay with the special food to avoid causing the pet discomfort
each time an allergic ingredient is fed.
While the pet is being tested for food allergies, it should
not be given treats, chewable medications, table scraps, or
rawhide toys that may contain an allergen.
To check for atopic and contact allergies, veterinary
dermatologists use an intradermal allergy test, or skin reaction
test. The pet is mildly sedated, a postcard-sized area on the
side of the pet is shaved, and small amounts of potential
allergens are injected into the skin on the shaved area. If the
pet is allergic to a particular substance, the skin will become
inflamed at the area of the injection.
Jeffers tested Nora, a wire fox terrier, for 58 different
allergens. The dog had been "scratching and biting herself
all over, 24 hours a day," since it was 3 months old, says
owner Katie Mathews of Bethesda, Md. "The scratching kept
Nora up all night and kept the family up all night," she
says. Before she was referred to Jeffers, Mathews had taken Nora
to several veterinarians, who prescribed various antihistamines,
shampoos, sprays, and a food elimination diet--none of which
worked. "Steroids were successful," says Mathews,
"but I didn't want to keep her on them because of the
long-term side effects." Mathews also "wanted to get to
the root of the problem" so that the allergic substances
could be avoided if possible.
Through skin testing, Jeffers determined that Nora had atopic
and contact allergies and was allergic to dozens of substances,
including pollens, molds, dust mites, grass, cotton, and wool.
Treating Allergies in Pets
Although allergies can't be cured, they can be controlled by
avoiding the allergens, treating the symptoms, or desensitizing
the pet. In Nora's case, all three methods are used.
Fleas, food ingredients, and some substances that trigger
contact allergies may be avoidable, but "with atopic
allergies, avoidance is virtually impossible," says Jeffers.
Drug products are available to relieve the symptoms of
itchiness and inflammation in pets. Like any drugs designed for
animals, these products must obtain FDA approval before they can
be marketed by meeting rigorous scientific standards similar to
those for human drugs.
The FDA approved two itch-relieving drugs in 2003: Atopica
(cyclosporine) for controlling atopic dermatitis in dogs weighing
at least four pounds, and Genesis Topical Spray (triamcinolone)
for controlling itching related to allergic dermatitis in dogs.
Atopica, a product of Novartis Animal Health US Inc. of
Greensboro, N.C., is a capsule given orally. It works by
inhibiting specific immune cells from reacting to allergens, and
can be given as a lifelong treatment. Genesis, made by RMS
Laboratories Inc. of Vidalia, Ga., is a steroid spray that is
applied to a dog's skin for up to 28 days. Both of these drugs
must be prescribed by a veterinarian.
The FDA has approved other steroid products for short-term use
in dogs and cats to relieve inflammation and itching. Long-term
steroid use is discouraged because these drugs work by
suppressing the immune system; this suppressant action over time
can leave an animal vulnerable to infection, diabetes, and other
conditions.
Veterinarians often prescribe antihistamines approved by the
FDA for humans to relieve itchiness in pets. Under the Animal
Medicinal Drug Use Clarification Act of 1994 (AMDUCA),
veterinarians may legally treat dogs and cats with drugs that
have been approved for people but not for animals. Pet owners
should check with their veterinarians before giving a pet any
human medications, including over-the-counter antihistamines.
"If we can control the allergies through medication for
occasional flare-ups, antihistamines and steroids are
useful," says Troutman. But if these medications are needed
continuously to provide relief, Troutman recommends seeking other
options, such as immunotherapy.
Immunotherapy is a treatment that stimulates the immune system
to decrease the body's reaction to allergens. Similar to people
with allergies, animals can be given immunotherapy, or
desensitization injections. These "allergy shots"
contain small amounts, or extracts, of the substances that the
animal is allergic to, based on the results of skin testing. The
owner gives the shots to the pet at home, usually in the scruff
of the neck. The extracts used for allergy testing and treatment
in veterinary practices are licensed by the U.S. Department of
Agriculture's Center for Veterinary Biologics.
Somewhere between 50 percent and 70 percent of dogs and 75
percent to 80 percent of cats respond to immunotherapy, depending
upon the study reported, says Morris. "Occasionally, it is
so effective that the animal is normal without other
treatments," he says, but the majority require medications
in addition to the injections. The injections are usually given
every 7 to 21 days, depending on the pet's response, says Morris.
And rarely does an animal become permanently desensitized so that
the injections can be stopped.
Nora gets a weekly injection. Mathews also gives her Atopica
and, when the pollen count is up, an over-the-counter
antihistamine. Mathews has placed synthetic blankets around the
house for Nora to lie on, since the dog is allergic to cotton and
wool in the furniture and carpeting. Nora also has a vinyl bed to
lie on in the yard, since she's allergic to grass. This allergy
management program helps keep the 18-month-old dog comfortable.
"She still has periods of scratching," says Mathews,
but "she's not biting herself as much and she's sleeping at
night." Mathews reports that her other dog, Nora's
littermate Nick, is allergy-free.
Allergies in pets are neither preventable nor foreseeable,
says Morris. "You can have one puppy out of a litter of 10
with allergic skin disease, or it can skip generations. We can't
possibly predict it," he says, even if you have a pet
examined by a vet at a very young age.
Pet Food: To Switch or Not to Switch?
Most experts agree that changing foods periodically will not
keep a pet from becoming allergic to certain ingredients.
"If you're genetically predisposed to develop an allergy
to something you eat, it will occur," regardless of
switching foods periodically, says Daniel O. Morris, D.V.M.,
chief of staff of the veterinary hospital at the University of
Pennsylvania in Philadelphia.
Morris advises against changing food ingredients at least for
the first year or two of a pet's life. "I see dogs,
especially, developing food allergies at very early ages,"
he says, adding that it's not a good idea to expose young animals
to many different ingredients.
"The gut lining in the intestinal tract is not fully
formed," says Morris. "The theory is that it allows
food proteins larger than appropriate to be absorbed." These
food proteins react with the immune system, causing an allergic
response.
If you know your pet has allergies to certain food
ingredients, read the food label carefully to avoid those
ingredients, Morris says. The front of a can or bag of food may
state one or two main ingredients, but the label will list a
number of others as well. "Changing brands does not
necessarily mean you're changing ingredients," he adds.
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