Allergies

Dogs and cats both are susceptible to various “allergies.”  We commonly see them occur in one of three varieties – atopy (pollen), food, and flea allergy.  The following discusses those three types of allergies.

Atopy

What is atopy?

Atopy is a hereditary disease that is one of the most common causes of itching in dogs.  Although it is seen in most every breed and mixed breed, it is especially common in terriers, Dalmatians, Schnauzers, and Poodles.  Dogs with atopy are allergic to various pollens, molds, and dust – just as people can be.  These items trigger allergic symptoms when breathed in or by just coming in contact with the skin.  People develop the typical seasonal “hay fever” symptoms of sneezing, runny eyes, and sinus problems.  However, these signs are minimal in dogs.  Itching is the hallmark of atopy in dogs.

What are the symptoms of atopy?

As mentioned above, itching is the main symptom of atopy.  Dogs typically will lick and chew their feet, rub their face with their paws or on the carpet and furniture, and in many cases develop generalized itching.  A few dogs will show additional symptoms such as sneezing and runny eyes but this is the exception rather than the rule.  This problem is rare in dogs less than 6 months of age and typically is first seen between 1 and 3 years of age.  Atopy tends to be seasonal and shows up whenever your pet is allergic to what is blooming.  However, when the offending agent is something like house dust itching can be year round.  In most cases atopy gets worse each year as your pet becomes more and more allergic to the pollens, molds, and dust that he or she is exposed to.

How is atopy diagnosed?

By far the most important aspect in the diagnosis of atopy is the history of seasonal itching involving mainly the feet and face.  Before we make the diagnosis of atopy in your pet we will want to rule out the many other causes of itching in dogs such as fleas, mites, food allergy, staph and yeast infections, etc.  This may require some laboratory testing such as skin scrapings, cultures, and in some cases blood or skin testing for allergies just like they do in humans.

How do we treat atopy?

In the treatment of atopy we have 2 basic options just like in people.  The first option consists of various drugs to stop the itching.  The second option is to do actual allergy testing to determine what your pet is allergic to and then start allergy injections every week or two.  The following outlines the basics of both methods:

Medications

In most cases we can use various combinations of medication to control the itching.  The following classes of drugs are ones we use by themselves or in combination with others.

1. Cortisone:  Cortisone drugs are very effective in treating itching associated with atopy in dogs.  Many dogs can be given an injection of long acting cortisone 1 – 2 times a year and effectively control their symptoms.  Other dogs will require more medication in the form of pills.  Side effects are minimal when these drugs are used properly.  We must be judicious in their use, however, since side effects can occur – especially at higher doses.

2. Antihistamines:  These drugs work wonderfully in humans, but not quite as well in dogs since histamine (hence the use of antihistamines) isn’t the only thing that makes dogs itch.  Only one in five dogs will respond to antihistamines of any type.  However, we like to use them when possible – especially in combination with fatty acids since their side effects are minimal compared to the cortisone drugs.  There are many different types of antihistamines we can use in dogs with atopy.  Individual dogs also show great variation in their response to the various antihistamines.  For these reasons, it is best to try several different antihistamines to see which one if any works best.  The antihistamines listed below are the ones you should try.  Use one for a week – if it works well in controlling the itching, then continue to use it.  If, on the other hand, poor or no improvement is seen – go to the next one.  The following antihistamines have been shown to work well in most dogs.  The first three are over the counter preparations available in generic form.  It is important to make sure the one you get does not contain other drugs for cold or flu relief which your pet will not need.

• Benadryl (diphenhydramine) – 1 mg/pound every 8 – 12 hours.
• Chlortrimeton (chlorpheniramine) - .25 mg/pound every 8 – 12 hours.
• Tavist-1 (clemastine) - .04 mg/pound every 12 hours.
• Atarax (hydroxyzine) – 1 mg/pound every 8 – 12 hours (prescription).
• Zyrtec (cetirizine) 10 mg – one pill for big dogs and ½ for small – once a day. 

The most common side effect of these drugs is drowsiness which usually wears off after several days of use. If any other side effects occur please call us.  It is best not to use these drugs in pregnant dogs, dogs with seizures, and when certain insecticides are used.  Just ask us if you have any questions about safety.

3.  Cyclosporine:  Recently a new drug has been very helpful in controlling the itching in dogs with atopy.  It is sold under the trade name Atopica, and has been a tremendous weapon in our arsenal as we try and keep our furry friends comfortable (and us sleeping) during the allergy season.  The drug is expensive and must be given daily for a month.  After that we gradually reduce the dose to once or twice a week – whatever is needed to keep those allergies under control.  In the dogs in which it works our clients are exceedingly happy.  It certainly is worth a try before we go to the expense of allergy testing and injections.  Cost is not that significant once we get past that one month induction phase.

4. Fatty acids:  There are two special fatty acids that are found in primrose oil.  Recent research has shown them to be very beneficial in dogs with atopy.  These fatty acids block the production of prostaglandins which is responsible for quite a bit of the itching in dogs with atopy.  When dogs are supplemented with these fatty acids – 20% need no other drugs to control itching, 40% are much improved and need fewer other drugs, and 40% don’t get any help.  These fatty acids also make antihistamines work much better than they would by themselves.  It is important to note that it often takes 2 – 3 months for fatty acids to reach their full effect.  We routinely recommend that ALL atopy dogs use them since their side effects are minimal, they are inexpensive, and most dogs take them easily.

Hyposensitization

This is recommended when atopy becomes so severe that your pet does not respond to the typical medications used to control itching.  In those cases we will do a blood test to determine exactly what things he or she is allergic to.  We will then have a “vaccine” made to vaccinate your pet with.  This will result in her becoming “immune” to the pollen he or she comes in contact with.  This method has an initial expense but is a very effective way to treat atopy and good to excellent results are achieved 80% of the time.  Before testing, your pet will have to be off of other medication for a period of time and we may want to run a food trial to rule out food allergy.  Points you need to understand are as follows:

• Initial testing to determine what he or she is allergic to costs $225.
• Initial starter vials cost $200 and will get us started for about 4 – 5 months.
• So, initial testing and starter vials have a start up cost of $425.
•  Follow up vials cost $200 and will last about 7 months
• You will have to learn to give your pet injections that initially will be done every three days, but long term it gets out to about every 3 weeks for maintenance. We will give you great instructions and demonstrate how to do the injections – it isn’t that hard! 
• If you are unable to give injections or don’t want to we can do that for you at a nominal cost.

Food Allergy

What is food allergy?  Food allergy in dogs and cats is more common than you would think!  It isn’t that your pet is allergic to all food – but rather is allergic to one or more protein sources that are found in dog and cat food. 

What are the symptoms?  When we see food allergy the primary signs are itchy skin and gastrointestinal upsets.  Not all dogs and cats have both problems.  Often, your pet may only itch or may only have intestinal signs.

Itching: Itching is one of the primary signs that we see in food allergy.  Things that make us suspicious of food allergy are:

• Non-seasonal itching:  Most allergies occur when the pollen count is high during the summer.  When we have a pet that itches during the winter when the pollen and fleas are gone – food allergy moves higher on the list of possible problems.
• Poor response to cortisone:  Most allergies to pollen and fleas will respond very well to cortisone injections and pills.  When we have a pet that has responded poorly or for a very short time to these drugs, we become suspicious of food allergy.
• Chronic staph infections & ear infections:  One of the common underlying causes of chronic recurrent staph infections or ear infections is food allergy.  When we get into a situation where these problems keep returning even with appropriate therapy we often will check into food allergy. 
• Facial itching in cats:  Interestingly, cats with severe facial itching often have food allergy.  It we see severe facial itching in a cat we often do a food trial immediately before trying other treatment methods. 
• Intestinal symptoms:  Vomiting and diarrhea are often seen in food allergy.  This is especially true in cats.   The symptoms are often chronic in nature and usually the animal does not feel that bad – they don’t act real sick.  Over time, however, we can see things like weight loss, blood protein loss, etc. 

How do we diagnose food allergy?  When we try and diagnose food allergy, it is often a diagnosis made my excluding other causes of itching.  In other words, we rule out other causes and then highly suspect food allergy.  Unfortunately, there is no reliable blood test for food allergy.  THE ONLY WAY TO DIAGNOSE FOOD ALLERGY IS WITH A DIETARY TRIAL FOR 10 WEEKS!    Itching due to food allergy often takes several weeks to disappear, so when we change diets you may not notice a change for a while.  We will prescribe a specific diet for your pet to eat as his is her ONLY SOURCE OF FOOD for at least 6 weeks.  During that time it is critical that you do not give any treats or let them have access to other food that your other pets eat.  That will completely invalidate the test.  You also must be careful not to feed any daily vitamins or heartworm prevention that is chewable – these often have beef in them.  The food we usually recommend is the one used by most veterinary dermatologists.  It is made with protein sources that your pet has probably never eaten and therefore will most likely not be allergic to.  These diets contain things like venison, duck, peas, & potatoes.  If all other potential causes of itching are controlled (infections, fleas, etc.), and you feed this diet, your pet should quit itching while on the diet - if food allergy is the problem.  If we are seeing intestinal signs as the symptoms,  they should disappear as well while on this diet.

How do we treat food allergy?  This is the good news!  We don’t need any lifelong medication to treat food allergy.  You just need to feed a diet that your pet is not allergic to.  You can keep them on the diet used in the trial forever (what most people do) or you can try other commercial diets that don’t have a lot of the proteins that were in the diet he or she was allergic to.  If symptoms return, however, you must switch back to the restricted protein source diet. 

Please call if you have any questions about this or any other problems.

Flea Allergy

All dogs and cats are irritated to some degree by flea bites, but some are actually ALLERGIC to flea saliva.  These animals have the same reaction to flea bites that we humans have to chiggers and poison ivy.  In these pets, A SINGLE BITE can elicit a reaction that itches for as long as a week.  The itching can be so severe in dogs that they literally scratch themselves raw.  This itching is seen initially over the back, rump, and hind legs – but can involve the whole dog.  This is also true for cats but they also have lesions around their neck and stomach.  Remember, these allergic animals do not have to be covered with fleas to have problems.  One or two can drive them crazy.  To treat animals that have flea allergy we usually use an injection of cortisone to relieve the itching followed by VERY EFFECTIVE FLEA CONTROL.