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Medicine: My itchy pet
How How many pet owners have watched their dogs licking their feet and thought that they were "bored" or think that when dogs rub their eyes, that they are sleepy? Only a small percentage of licking, chewing, rubbing, and scratching are actually due to behavioral issues. Instead these are signs of an itchy animal. This article deals with why our pets itch, and what we can do to stop their discomfort.
Pets are similar to their owners in a lot of different ways. Unfortunately, one way in which they are similar is that pets also suffer from allergies, just like people do. While cats can and do get allergies, they are much more common in dogs. More dog patients that we see here have allergies than do not. Just like in people, allergies have different causes and range in severity. In this newsletter, we will discuss possible causes of allergies and what things can be done to help our itchy companions.
First of all, dogs, cats, and people all respond to allergies differently. Humans primarily get hay fever, itchy eyes, congestion, runny nose, and asthma/bronchitis. They also can get itchy skin and seborrhea, which is called atopic dermatitis. Cats get primarily respiratory problems, such as bronchitis or asthma and can get some itchy skin as well. Dogs primarily get itchy skin and ear problems, but can get respiratory symptoms on occasion. What causes allergies? Allergies are caused by proteins in the environment activating a special type of antibody from certain immune cells. This antibody activates other cells, causing histamine release, which causing an inflammatory reaction. This is a gross oversimplification, but the immune system is quite complex and too lengthy to go into detail. There is a "threshold effect" theory, in which if there is enough stimulation by these proteins (called antigens or allergens), then a line gets crossed and symptoms start. This is why, with people, certain foods cause them problems when they are sick but not other times.
What are the different
antigens that cause allergies in our pets? There are four major groupings:
These are allergic reactions from insect and arachnid bites. Flies, mosquitoes, mites, spiders, ticks, and most commonly, that pesky flea. Flea allergies used to be the most common allergy in dogs and cats. Since Advantage and Frontline came on the market in the early 1990's, it is now uncommon to see this. In dogs, the symptoms generally involve the area over the back, near the tail. We see extreme itching and hair loss in this region. In cats, we see scabs all over the body, but generally on the head and neck region.
Environmental or Inhalant allergies:
These are the most common allergies and are caused by proteins found in the air, although there is some debate about transmission through the skin. These proteins are grasses, pollens, weeds, dander (dog, cat, human, rabbit, etc.) tress, molds, and insect residues. Inhalant allergies are now the most common allergy that we see in dogs. They are rare in cats, and usually cause a severe asthma. If your cat is coughing, you need to seek veterinary care for him/her immediately. With dogs, we almost always see skin problems. Most of you who own dogs may notice that they tend to lick their feet a lot, or are getting a coppery color to their fur on their feet. This is not boredom. They itch. Foot licking is the most common sign of atopic dermatitis (atopy), or inhalant skin allergy. We also see chewing/scratching at the face, armpits, groin, red irritated eyes, skin infections, and ear infections. The fur can become quite discolored from all of the saliva that is deposited during licking and become a copper color. Symptoms of atopy can be mild to severe, so bad that they would rather scratch than eat and rip themselves raw. Sometimes the only sign of atopy in dogs is chronic ear infections. Because not all of these antigens are present all year, atopy starts out as a seasonal problem. But with time, it becomes worse and worse, until it is a year-round issue. We normally start to see this problem starting to develop at around 1-2 years of age.
Bacterial hypersensitivities:
Dogs and cats are covered with bacteria and yeast. This
is a normal part of the skin (even yours). Sometimes our pets can develop
an allergic reaction to these bacterial proteins. Bacterial allergies
can be difficult to distinguish from other forms of allergies. Generally,
we become suspicious after recurrent skin infections occur. There is a
blood test for this problem. Luckily, this problem is rare.
Food sensitivities:
Any ingested protein can cause an allergic reaction. It
can be from any protein in the diet, even one from the same food that
they have been on for years. Common ingredients such as chicken, beef,
corn, rice, lamb, wheat, and preservatives have been known to cause reactions.
These ingredients are found in almost every food. Some people believe
that lamb is good and corn is not. This is a myth. Corn is bad only to
pets allergic to it and lamb is only good if the pet is allergic to another
protein source such as beef. The lamb and rice diets that came out for
dogs and cats with food allergies years ago are no longer effective because
they are found in so many foods now. Food allergies follow no distinct
pattern. They can affect any part of the body and can be difficult to
distinguish from other forms of allergy. It can occur in dogs and cats.
It can also have a gastrointestinal component as well, with chronic vomiting
or diarrhea. Luckily it is rare.
It's important to remember than pain is easier to tolerate
than itching, which is why dogs and cats rip themselves raw when having
an allergic skin problem. The same thing happens when you are scratching
at a mosquito or fleabite if you are allergic to them. Allergies have
no cure but there are several ways to combat them. We will address them
by category:
Before good flea control was available, we needed to use long-term corticosteroids. This is no longer necessary for most pets. Monthly flea control with Frontline or Advantage is all that is usually required. Don't bother with pet store brand topical flea products. They generally do not work well and can be toxic. Both Advantage and Frontline are new products and work well. They also target an enzyme found in insects but not mammals, making them safer. In our opinion, while Advantage works a little faster, we like the Frontline because it affects both fleas and ticks and pets can safely swim or be bathed without diluting the dose. Program and Sentinel also work, but not as well in dogs with allergies. These are oral products that work by sterilizing the flea when they bite. This bite allows the allergy to still occur.
Food allergies:
Food allergies do not respond well to medications. There
is no good, reliable test for food allergies. The blood tests are unreliable
and we do not use them. The test of choice is a food trial. We use two
types of food for the food trials. One is what is called a Novel Protein
Diet. This is a diet comprised of proteins not found in other foods. Some
examples are kangaroo and oat, venison and potato, rabbit and potato,
duck and potato, and fish and potato. These foods work because if your
pet has never eaten the ingredient, they cannot have the antibodies that
cause the allergies. The other food has proteins that are so small that
antibodies cannot attach and therefore no reaction can occur. These foods
need to be used for 8 weeks with no other foods or treats given, as it
takes a long time for these proteins to leave the body. The diet is very
strict. If this cures the itching, than we know that the allergy is diet
related. At this point, we choose to continue the diet indefinitely, or
we can do a challenge. This challenge is performed by slowly re-introducing
ingredients back into the diet one at a time. When the offending protein
is re-introduced, itching usually ensues within a few days. We then make
sure that they do not eat that ingredient again.
Bacterial hypersensitivities:
These are difficult to control. We need to rule-out other
allergies and once we have done so, we treat the cause: the bacteria.
We use topical shampoos, conditioners, and soaks. We also use long-term
oral antibiotics. Sometimes we use a product called staphage lysate, which
is an injection of the toxin that the bacteria produces. Why this works
is a subject of many theories by dermatologists. It helps about 1/3 of
dogs with this problem. Unfortunately, sometimes long-term medication
is the
only solution.
Inhalant
Allergies: Many years ago, our only recourse for these was
long-term corticosteroids. If you read the article on Cushing's Disease,
you know that this treatment option causes a lot of complications. These
days, long-term corticosteroid treatment is a last resort for dogs with
this type of allergy. If your vet is treating itching with steroids alone,
without other measures, then you might want to talk with them about other
treatment options available. Avoidance does not help much, unless they
have a grass allergy, in which case avoiding grass helps a little. What
we do for dogs to aid their skin problem is broken down into acute and
long-term care.
Acute:
We need to get these dogs feeling better fast. This means
corticosteroids. But only for a short time. We also need to get under
control secondary skin and ear infections, which means antibiotics, antifungal
medication, and/or shampooing. Once they are over their severe itching,
we move into the long-term therapy.
Long-term: Since long-term corticosteroids
have many undesirable side effects, we need other options.
For mild cases: shampooing is very important. We recommend weekly
shampooing with cool to lukewarm water, letting the shampoo sit on for
5-10 minutes. We recommend using hypoallergenic shampoos such as Hy-Lyt
or Allergroom, colloidal oatmeal shampoos, or a new anti-itching/anti-inflammatory
shampoo called Allermyl. Also we sometimes recommend using baby or diaper
wipes between the toes every evening. Fatty acid supplementation also
helps to decrease inflammatory mediators in the skin. These are Omega-3
fatty acids derived from flaxseed and marine oils. Omega-6 fatty acids
help to moisturize the skin and coat. The fatty acids we like to use are
called Derm Caps, and they come as a liquid to squirt on the food and
as an oral capsule. These contain both types of fatty acids. The Eukanuba
Fish and Potato diet is also high in omega-3 acids, and is good for dogs
with inhalant and food allergies, and in dogs that don't like medicine.
Topical steroid conditioners, such as Resicort work well as well.
For more severe cases: We still do the same treatment as for mild
cases, but we add more medications. If the problem is only for 1-2 months
out of the year, we can use corticosteroids at a very low dose every other
day. If it is more than that, we like to use antihistamines. Antihistamines
help to block histamine, a compound instrumental in causing allergic reactions.
Unfortunately, this effect is not as good in dogs and cats as it is in
people. The antihistamines also cause sedation, which is a good side effect
to help reduce itching. Because they lack this effect, the newer antihistamines
for people, such as Zyrtec, Allergra, and Clarinex are not that effective
in our pets. Antihistamines help about 30% of dogs with inhalant allergies.
They work best if used all the time during the allergy season, not when
an outbreak is occurring. The most effective antihistamine is Hydroxyzine.
This medication works best given every 8 hours. We use it commonly because
of low side effects and cheap cost. Unfortunately, the price of this generic
drug skyrocketed recently. There are other antihistamines available as
well. Soon a different formulation of Hydroxyzine will be available.
Severe cases:
For dogs that are still itchy we recommend allergy testing and allergy
shots. The testing can be done via a blood or skin test. We perform the
blood test, as it is almost as accurate and less invasive than the skin
test. The skin test requires sedation, is quite expensive, and can cause
a severe allergic reaction. The blood test is less expensive, easier,
and does not require any sedation. Also the skin test cannot be used with
dogs that have recently had corticosteroids, whereas the blood test can.
Both tests look for allergy antibodies to weeds, trees, bushes, dust mites,
dander, mold, and insects common to this area. If you know of any plants
or animals near your home, these are always helpful to add to the test.
Once we know what the dog is allergic to, we have an allergy antigen serum
made. This is injected under the skin and we try to teach pet owners how
to do this at home. Eventually, our goal is to give a shot every 14-20
days. The only side effect is the possibility of an allergic reaction.
Luckily these are quite rare. About 70% of dogs are symptom-free on the
shots and need no other medications that shampooing and the fatty acids.
The younger we start the shots, the better the response. Of the dogs that
don't respond 100 %, antihistamines work or intermittent steroids work.
Sometimes no matter what we do, we can't stop the itching. These dogs
have to be on long term corticosteroids and we reduce the dose to as low
as possible. As a side note, Bishon's are only about 50% responsive to
the shots. Sometimes, we need to re-test dogs on the shots, as with time,
they can develop allergies to more proteins in the environment.
New developments:
Recently, there have been new advances in the fight against allergies
for dogs that have not responded to other treatments. This is an ever-changing
area and with time we will get better and better control. These newer
drugs are used off-label, which means that they are not FDA approved for
dogs and/or for that specific purpose. Does that mean that they are dangerous?
No, most likely not but while dermatologists have done studies and the
drugs used for a long time, they have not undergone the rigorous safety
studies the FDA requires.
- Amitriptyline (Elavil) is an anti-depressant with antihistamine properties as well. We have found good success with this medication especially in dogs that may also have some anxiety driving their scratching. It is given twice daily. It is now generic, which has reduced the cost greatly.
- Pentoxifylline is an anti-inflammatory that blocks the cascade responsible in inflammation, especially in white blood cells in the skin responsible for allergies. It also helps repair damaged skin where blood vessels have been damaged. It has been found to work best in conjunction with other treatments. It may cause mild gastrointestinal side effects. It is given three times daily.
- Cyclosporine is an immune suppressive drug. It is used frequently with people and pets that have undergone organ transplants. It is used with dogs with "dry eye" as well. It helps to decrease signals in certain types of immune cells, which cause allergies. The drug is VERY expensive, but may be an alternative for your pet. It can react with many medications, so a careful medication history must be taken. It is best given apart from meals. The biggest side effect is vomiting. Because it can suppress the immune system, frequent lab work must be taken with dogs on this medication. It is good for dogs, which nothing but long-term steroids has helped. It works best on dogs with year-round itching. It is given once daily at first, but hopefully later given every other day.
Unfortunately, dogs and cats don't always follow the textbooks. They can
be allergic to many things, such as a dog with flea allergies, atopy,
and a beef sensitivity. These are hard to diagnose and treat. Sometimes
if we treat one cause, the allergies are controlled. Sometimes we need
to treat all. For that reason, all allergic dogs must be on monthly Frontline
for flea control. If the shots don't work for inhalant allergies, we sometimes
try a food trial. It is sometimes more art than science to control allergies.
Not all dogs are helped by the same protocol, so trial and error has a
big part in defeating allergies for your dog.
Dogs with a low thyroid level, or hypothyroidism, have worse allergies. When we treat for chronic allergies in dogs, we always like to check their thyroid levels. If there is a problem, we treat with oral synthetic thyroid supplements. There will be an in depth discussion about thyroid disease in an upcoming article.
I hope that this helps
you understand a little more about allergies and our pets. Please call
or e-mail us if you have any questions.
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