Tuesday, February 12, 2013

More Allergies

How can we test my pet for what they are allergic to?

The first point to be made about allergy testing is that testing should only take place after a diagnosis of an airborne allergy is made.  A diagnosis is made by clinical signs and your pet fitting many of the criteria that have previously been discussed.  The reason that a diagnosis should be made first is testing is not 100% accurate and there is the possibility of false positives.  This means that pets without allergies can have positive responses to allergy testing.  The second point to discuss before testing is why we are testing.  The reason we are performing “allergy testing” is to identify what allergens are causing a problem, so we can make a solution with these allergens to perform immunotherapy.   We will talk about immunotherapy shortly.

There are two ways to test for what your pet is allergic to:

      Intradermal skin testing (IDST): For this procedure your pet is sedated and a patch of hair is shaved on his/her side.  Small amounts of concentrated allergen (pollens, molds, grasses, weeds) extract are then injected under the skin and the reaction to the allergies are measured.  Allergens that your pet is allergic to should puff up and become red.  In order to get accurate results on these tests your pet will need to be off of antihistamines for a minimum of 2-4 weeks and off steroids for at least 4-6 weeks.  This testing does typically require referral to a veterinary dermatologist and the usual cost is ~$380.  This is considered the “gold standard” for allergy testing.  The best time of year to test is usually in the early fall (Sept/Oct).

      Serum antibody testing: This is a different way of testing for allergies in pets.  The pros of this test is that it does not require referral, only requires a blood draw, and typically your pet does not need to be off of steroids or antihistamines for testing.  The drawback is that you can have some false negative or positive results (this is true for any testing).  For this test the amount of antibodies (specifically IgE which is associated with allergies) to specific allergens are quantified.  Those allergens with higher antibody levels are deemed the problem allergens.  The cost for testing is ~$200.

It is possible with both tests to get negative results (no reaction to allergens).  For dogs that obviously have an allergy problem there can be a few reasons for negative tests including:
1. Improper withdrawal of steroids/antihistamines
2. Wrong time of year for testing
3. Improper choice of allergens being testing

If your pet has a negative allergy test, then it may be suggested to try the other type of testing (IDST versus serum testing or vice versa).

My pet had allergy testing performed, now what?

Once your pet has been allergy tested and the offending allergens are identified, then we can proceed to immunotherapy.  Immunotherapy involves making a solution that contains small amounts of the different allergens that your pet is allergic to.  This solution is then injected under the skin (or more recently placed under the tongue) every few days.  There is an initial induction phase (6-10 weeks) where the solution is dilute and then over the next few weeks the amount given and the concentration of the solution are increased.  Once we have reached the maintenance phase, your pet will be getting injections every 1-2 weeks.    Many dogs (60-70%) show improvement with immunotherapy.   This does not necessary mean that the itching symptoms will go away completely.  In many cases, pets may need additional therapy (anti-histamines or steroids) during certain times of year, but hopefully the dosage, frequency and length that these medications are needed will be reduced.   The improvement are not immediate either.  Pets typically take 3-5 months to show improvement and in some cases can take upwards of a year.  The cost per year for a typical dog on immunotherapy is ~$620.  This therapy is typically continued life long, but in some instances can be stopped after a few years of therapy.

Tuesday, February 5, 2013


Although it is not the time of year for allergies to hit, it is always a conversation I have with owners (whether it be at work or when I mention I am a veterinarian to something).  I figured it would be a good topic to hit on.

Is my pet allergic?

Most people are familiar with allergies in people and may even have allergies themselves.  They avoid going outside in the spring when the trees are pollinating or don’t go over to a friend’s house because of a pet.  Who wants a runny nose anyway?  Well, dogs and cats can also have allergies, but instead of runny noses or sneezing they tend to get problems with their skin, specifically itchiness.  It can make pets miserable at times, but fortunately we have ways to help relieve some of the symptoms and in some instances can almost cure the condition.

Well, is my pet allergic?

If you think your pet is allergic because they are itching a lot and go to the veterinarian’s office, they will likely ask you a series of questions to get a handle of what is going on.  There are some common criteria that environmental allergies fit into:

Young age of onset: Most pets with airborne allergies start showing symptoms between 6 months and 3 years.  It is typically after the second exposure that symptoms develop.
2.      Seasonality: Airborne allergies typically show up during certain times of year.  Spring is bad for tree pollens, summer for grass, and fall for weeds.  However, if your pet is allergic to dust, dust mites, food mites, or molds, then they may have year round problems.
3.      Response to steroids: Itchiness should respond very well to steroids in allergic pets.
4.      Areas of itchiness: Pets who have localized itchiness in their feet (imagine white dogs with brown feet from saliva staining) typically have an allergy.  Other common areas are the arm pits, feet, around the muzzle and eyes, ears, and butt area.

What are some other possibilities for my pet’s itchiness?

Airborne allergies are not the only cause for itchiness in pets.  There are other things that can cause itchiness as well and should be considered or ruled out before treating your pet.  This may require a few simple tests including cytology of the skin and a skin scraping (both look at material on the skin under the microscope).  Here are a few things that we try to rule out:
      Other allergy: Pets can have allergies to other things.  The other more common allergies include flea allergies and food allergies.  There are a number of good flea preventatives that can be used along with treating the local environment that can help rule this out.  A “hypoallergenic” diet for 8-10 weeks without any other food sources can rule out a food allergy.  Of course it is not that simple as pets can have multiple allergies as well.
2.      Simple infection: Pets can get infections with yeast or bacteria that can mimic allergic symptoms.  Treating for the infection with resolution of the itchiness and no recurrence is a good indication that the problem was an infection.
3.      Scabies: These are mites that live in the outer layer of the skin.  If these are causing a problem, then all pets in the house are typically itchy, you may be itchy, and typically the ears and elbows are more affected.  Treating with a trial of Revolution (topical spot-on product) for three times two weeks apart can rule this out as skin scrapings don’t always uncover these mites

OK, we are pretty sure my pet is allergic to something in the air, now what?

Once we have come to the diagnosis of an airborne allergy there are a few ways of tackling the problem.  The main ways of helping your pets are 1.) Symptomatic therapies 2.) Avoiding the offending allergen 3.) Allergy testing with immunotherapy injections.

What are the options for symptomatic therapies?

There are a number of drugs available that can help with your pet’s itchiness.  The first thing that we would want to do is treat any concurrent infection.  This is typically done with a combination of oral medications (antibiotic or anti-yeast depending on the problem) and shampoos.  Once we know any infections are under control, then we can try and control the itchiness.
      Antihistamines: Although these are not the strongest against fighting the itch, some pets (~15%) respond very well to antihistamines.  I typically recommend trying the medication for 7 days to judge whether there is a response.  Some pets respond better to one antihistamine over another, so you may want to try a few before judging whether or not they help.
a.      Loratidine (Claritin): 0.25 mg/lb once daily, available 10 mg tablet
b.      Cetirizine (Zrytec): 0.25 mg/lb once daily, available 10 mg tablet
c.      Diphenhydramine (Benadryl): 1-2 mg/lb 2-3 times daily, available 25 mg tablet
d.      Chlorpheniramine: 2-12 mg total dose 2-3 times daily, available in 4 mg tablet
e.      Fexafenadine (Allerga): 0.5-1 mg/lb once daily, available in 30 mg (children’s strength)

2.      Steroids: The typical one used is prednisone.  These typically work better than antihistamines to help relieve the itch; however, they do tend do have more side effects.  Minor side effects can include drinking and urinating more, eating more, and occasionally a personality change.  More serious side effects (typically happen when on chronic steroids) are immunosuppression, muscle loss, and making prone to diabetes.

3.      Omega fatty acids: These are typically given in the form of fish oil.  They interfere with the inflammation of the skin that is causing the itchiness.  The usual dose is around 500 mg per 20 lbs, but it is hard to overdose with this medication.  The 500 mg is the active ingredient (DHA + EPA), so make sure you look at the label on the back as it can differ from total mg label on the front.  Usually a double strength product is best.  These can be given whole or broken over the food.  There are also specially formulated foods that have higher doses of omega fatty acids that can be tried (i.e. Hill’s J/D).

4.      Cyclosporin: This medication works very similar to prednisone by suppressing the inflammation in the skin causing the itchiness.  The advantage over steroids is a reduced amount of side effects, particularly the drinking and urinating.  The major downside is cost.  At full strength for a typical 20 lb dog the cost per month is ~$115.  This is typically the starting dose and many times can be reduced after a month or two, but you are still looking at a minimum of ~$65-70 monthly.

5.      Topical therapy: There are many products that can be used topically that help with allergies (shampoos, conditioners, etc).  Recently, a new theory that allergic pets are deficit in certain proteins in the skin has emerged and in response companies have made topical spot-on products to help supplement these deficiencies.

I will talk a little more about allergy testing and immunotherapy in an upcoming post.  I thought this was enough to talk about for now.