Allergic Dermatitis

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Introduction

Allergies are one of the most common causes of skin conditions. They are encountered in pets, especially dogs, as often as we see them in humanoids. The main difference between us and pets is that allergies in pets tend to cause skin conditions.

This type of allergy goes by several names, the most common are atopy, allergic skin disease, or allergic inhalant dermatitis.

Allergies can be hard to control and are chronic in nature. This causes significant frustration for pet owners and discomfort for pets. A correct diagnosis along with proper therapy instituted early in the course of the disease will minimize this frustration.

This page summarizes and generalizes the complex problem know as allergic skin disease. It is detailed, and will take a few minutes of your undivided attention to help in understanding this problem.

In the beginning of this page we will give you the background of their causes and how we diagnosis them. We will talk about treatment towards the end. If you want to skip the background and proceed right to treatment click here.

 


Pathophysiology of Allergies

When the immune system encounters an allergen that has the potential to cause disease (ex. parvo virus) it produces antibodies called IgG (immunoglobulin G, previously known as gammaglobulin) and IgM (immunoglobulin M). For the first 7-14 days of infection the virus spreads throughout the body because not enough antibodies are produced to stop them. Within 7-14 days enough antibodies are made to neutralize the virus, and the pet eventually recovers from the disease, all other things being equal.

As time goes on the now sensitized immune system is ready to produce large amounts of antibodies rapidly the next time it encounters this virus. The rapid antibody response neutralizes the virus immediately, instead of taking the 7-14 days that occurs the first time it encountered the virus. This is called the anamnestic response, and is why a pet that recovers from parvo virus does not get the disease again.

A different scenario presents itself when the immune system encounters an allergen that is not necessarily pathogenic (ex.- a pollen particle). A different part of the immune system kicks into high gear when these non pathogenic allergens invade the body.

When a pollen particle enters the body for the first time (through the skin or respiratory passage) it stimulates the body to produce antibodies also, this time they are called IgE (immunoglobulin E). This IgE antibody attaches to the allergen in order to neutralize it, just like IgG would do to a parvo virus. This process, called sensitization, occurs in the first season a pet encounters a specific allergen in its area. Without this sensitization there is no allergy.

The next time a pet encounters these pollen particles (usually the next allergy season) the immune system produces large amounts of IgE antibodies rapidly because it has been sensitized to them from the previous season. Again, this is similar to what happens when the immune system makes IgG and IgM antibodies against parvo virus.

IgE, with attached allergens, circulates throughout the bloodstream to a type of cell called the mast cell. Mast cells contain many chemicals that can cause inflammation, the most important of which in relation to allergies is called histamine. When an IgE antibody (even IgG can be involved)) with an attached allergen encounters a mast cell under the skin, it alters the membrane of the cell, and histamine leaks into the surrounding tissue. Histamine causes inflammation, noted as redness (erythema) and itching (pruritis) on the skin surface. The reaction that is seen on the skin surface is called a wheal or a hive. This causes your pet to lick, scratch, or bite at this area which now itches.

It is the mast cell, that releases histamine when it encounters an IgE antibody with a pollen particle attached, that is a major component of allergies. This is what occurs in atopy and is suspected to occur in food allergy. In flea allergies, it is an allergic reaction to the flea saliva that causes the immune system reaction.


Types

There are 3 main types of allergies in relation to skin conditions. It is possible for a pet to have a combination of all 3 allergy types. A pet that might not be scratching excessively because it has a minor food allergy can start scratching uncontrollably if it is bitten by a few fleas. Flea control is crucial in southern California. Detailed instructions on how to control them are on this page.

1. Food Allergy

They are caused by an allergic reaction to ingredients or preservatives in food. Some of the more common food allergens are:

horse meat eggs
beef fish
pork corn
lamb soy
poultry products preservatives and dyes
dairy products rawhide chews and dog biscuits/treats

In dogs, beef, dairy products, and wheat tend to cause most of the problems, with chicken, lamb, and soy following. In cats, beef, dairy products, and fish account for most of the food allergies. Premium dogs foods can contain these products, so just because you are feeding a higher quality or more expensive food doesn’t mean that food will not cause a food allergy.

It is estimated by some veterinary dermatologists that food allergies account for only 10% of all the allergies that cause allergic dermatitis. In those pets that truly have food allergy, a high percentage also have atopy at the same time. Cats might have more food allergies than dogs.

Dog owners commonly go to pet stores to get food to stop their pet from scratching. Pet store employees will recommend a specific food to stop the itching because they are under the assumption that this is the main type of allergy that causes skin conditions in pets. Pet stores see food as a major profit center, so they will tell you a certain type or brand of food will cure your pets skin (and other) conditions. The employees of these stores have no business giving advice unless they are licensed veterinarians,  and have discussed with you the following points that are so important in making a diagnosis of allergic dermatitis:

Your pets predisposition to certain diseases, including allergies. Please click here to learn more about what diseases specific dog and cat breeds are prone to .

Your lifestyle and your pet’s lifestyle

The specific history of your pets skin condition- time of year, where they are itching, etc.

Results of a thorough physical exam checking all organs besides skin

Diagnostic tests to eliminate internal (hormonal etc.) and external (mites for example) causes of skin conditions, and analyze the internal organs.

The efficacy of prior treatments

The effects a change in diet will have on other organs besides the skin

Your flea control program

To learn much more about nutrition as it relates to skin conditions please read our Nutrition Page.

2. Flea Allergy Dermatitis (FAD)

When a flea bites a dog or cat it is looking for a meal of blood in which to nourish itself. In order to suck this blood it inserts an anticoagulant into its saliva to prevent the blood from clotting while it sucks it through its small proboscis. It is the allergens in this saliva that cause an allergic reaction to occur.

Fleas are a huge and overlooked cause of skin conditions in dogs and cats. On almost a daily basis we are presented with pets that are scratching uncontrollably with an owner telling us they use flea control and their pet has no fleas. Our physical exam proves otherwise.

With the advent of new treatments that are convenient and very effective, this problem is easily controlled compared to the shampoos, powders, sprays, and bombs we had to use in the recent past. The products we recommend are oral Trifexis and Comfortis in dogs and  topical Revolution in cats. In addition to excellent flea control these products also prevent heartworms and intermal parasites like Roundworms. Revolution in cats even controls scabies.

We also have many other products available to suit your needs. Our staff has detailed information to give you on these products along with others to help you make the right decision for your circumstances. It is critical in southern California to use these products year round. This is the most effective way to rid fleas from your environment. Far too many people use flea products only in the warmer months. It will take these products several months to rid your environment of fleas once you restart them, which means your pet will be miserable during this time.

Here is a checklist of what you can do to take care of your pets flea problem.

  1. Use your flea products year round. This step alone will probably solve your problem. Since many flea products do more than control fleas your pet will also be healthier regarding heartworm and internal parasites (worms).
  2. Flea comb your pet before your bring it into your house after it goes outdoors, especially a dog park or similar area.
  3. Vacuum your household carpet, where your pet sleeps, furniture, rugs, and flooring daily. Find where your pet’s fur accumulates, and go under baseboards, ventilators, and furniture. Pre-adult fleas like darkness so vacuum under beds and cracks in your wood floor.
  4. Put a flea collar or flea powder in the vacuum cleaner bag. Put the flea infested bag in a sealed plastic container and discard.
  5. Wear white socks and walk around your house to see if fleas jump on your socks as a way to monitor.
  6. Use borate powder products, a non-toxic powder, that desiccates the fleas in your carpet.
  7. Wash your pet’s bedding in hot water and let it soak in soapy water for at least 15 minutes prior to washing.
  8. Time routine bathing for just prior to when your next topical flea product application is due to maximize its effectiveness.
  9. If visitors bring their pets over make sure they are flea free by requesting them to be treated prior to a visit. Fleas on visiting animals do not usually jump from pet to pet, but they will contaminate the environment.
  10. Treat all pets in your house. This commonsense suggestion is often overlooked.
  11. Clean your car and pet carriers
  12. Treat your immediate outdoor environment if that is a continual source of new fleas.
  13. Feral dogs, cats, raccoons, and opossums that take up residence or roam through your yard need to be controlled. Rabbits and squirrels are seldom a source of fleas.

3. Atopy or Allergic Inhaled Dermatitis

Canine atopy is a genetically determined predisposition to produce IgE antibodies when exposed to an allergen. Re-exposure to this same allergen in the future causes allergic skin disease (you learned the mechanism above). Depending on the study, it is estimated that between 3% and 15% of dogs have atopy.

Common allergens that cause this reaction are ragweed, pollen, house dust, house dust mites, mold, animal dander, feathers inside the house. Outside its grasses, trees, and shrubs. The allergens can be inhaled, pass through the pads of the feet, and even possibly ingested. Since these compounds are in abundance everywhere, it is apparent that preventing exposure in the first place is difficult.

If fleas are not a factor, atopy accounts for up to 90% of the allergies that cause allergic dermatitis. Only a small percent of these pets with atopy also have a food allergy at the same time.


Symptoms

The most consistent symptom in pets with allergic skin disease is excessive itching. The medical term for this is pruritis. High strung dogs might itch more than placid dogs. Chewing, biting, or licking, or rubbing the skin can all be manifestations of pruritis.

Dogs can chew so incessantly that they wear down their incisor teeth to the gumline

 


In dogs some of the more common areas for pruritis to occur are the face, feet, and armpit areas. As the problem progresses the whole body might be involved. Some pets will scratch excessively but not show any problems with their skin.

If your pet has an allergy to fleas you might find tiny blood spots where it has layed down. These are the result of flea dirt that has fallen off your pet and become wet. Since flea dirt is made up mostly of blood that the flea has sucked out of your pet and has passed through its digestive tract, they appear as small blood spots on the floor or table tops when wet.

Other symptoms can include:

The slight redness (erythema) to the face of this dog.

 


The dark, stained areas on this poodle’s foot are due to excessive licking. The color change is due to the chronic saliva on the hair, and the changes it causes on the hair coat.

 


This dog’s skin is oily from chronic rubbing.This loss of hair is called alopecia.

 


This Golden Retriever has significant redness (erythema) on its ear flaps. Chronic ear inflammation or infections can be a sign of atopy.


The above pictures were all caused by atopy. They could have been caused by other diseases though, so you cannot make a diagnosis of a skin condition just by looking at them.

Cats get skin allergies also, although not as frequent as in dogs. They might exhibit the same or different symptoms. Different symptoms include tiny bumps throughout the body, ulcers on the lips, excoriation of the neck, and even patches of missing hair (alopecia) without any skin lesions. Ear problems related to allergies are rare in cats compared to dogs. Cats get a problem called psychogenic alopecia that can be similar in appearance to atopy.

It can be difficult to tell pruritis from normal feline grooming. Vomiting hair balls, hair in feces, and hair in your cats mouth when you brush its teeth (you are doing this aren’t you?) are all clues.

This cat has an allergy that caused it to irritate the skin above its eye by rubbing its face

 


This is a severe version of an ulcer on the lips. It is called the Eosinophilic Granuloma Complex.

 

 


Diagnosis

Since the symptoms of allergic skin disease mimic those of other skin diseases, a thorough approach is needed to differentiate them. In every disease we encounter we follow the tenets of the “diagnostic process” to ensure that we make an accurate diagnosis, and that we do not overlook some of the diseases that are also encountered in conjunction with skin diseases.

1. Signalment

Typically, atopy occurs in mature dogs between 1- 3 years of age, although it can occur earlier (Shar pei’s can get it as early as 3 months). The condition rarely starts in dogs over 6 years of age.

Most dogs get their first exposure to an allergen and develop sensitization in their first exposure to a pollen season. Symptoms usually occur during their second season of exposure to the pollen allergen when the immune system has its exaggerated response to the allergen and produces high levels of IgE. Dogs that are highly allergic can show signs of atopy during their first season of exposure to pollen allergens. It depends on how long the pollen season lasts and how rapidly their body produces the IgE antibodies.

Several canine breeds are prone to getting atopy. They include, but are not limited to:

Terriers Beagle
Retrievers Setters
Lhasa apso Miniature schnauzer
Shih Tzu Pug
Cocker spaniel Boxer
Dalmatian Shar Pei

 


2. History

Atopy tends to be a progressive disease with worse symptoms each allergy season. Many dogs will be more affected during a specific season. As time goes on dogs can have allergies year round. It is not a contagious disease, so other dogs, cats, and people in the same household do not usually have symptoms (unless of course it is another dog that is highly prone to allergies).

The progeny of atopic dogs are more prone to developing atopy than other dogs. Careful breeding therefore can help minimize the occurrence of this problem.

Pets that have been treated with cortisone in the past, and did not improve, give us a clue that something else besides an allergic disease is involved.

Food allergies in dogs and cats can start at any time in a pet’s life, even those on the same diet for a long period of time. Non-seasonal allergies bring food allergies to mind, along with vomiting or diarrhea, although these are not consistent findings. The skin lesions in food allergy are indistinguishable from atopy, but have a propensity to show only inflammation of the ears. Feeding dog and cat foods that contain ingredients that pets are routinely allergic to might also clue us in to a food allergy. This includes the premium foods and those that contain lamb.

Flea allergies are suspected whenever we are presented with a pet that has a skin condition and is not on routine flea control. This is true even for pets that never go outside. Other pets in the household that are itching might also indicate fleas in the environment. Flea allergies routinely cause hair loss at the lower back area (called the dorsal-lumbar area), which is not typical of atopy and food allergy.

3. Physical Exam

The physical exam of a dog with a skin condition is the same as any other sick pet. We examine the whole body for clues as to the cause of the skin condition. The distribution of the skin lesions gives us a clue as to the cause, but is not consistent in all skin conditions.

Some of the more common exam findings are:

Pyoderma

This dog has licked so much it has maimed itself, and now has pyoderma, which is a skin infection.


Conjunctivitis

This is an inflammation of the eyes. The green discharge in the corner of the eye is from fluorescein stain that was checking for a scratch on the cornea.

 


Lichenification and hyperpigmentation

Chronic licking and scratching can cause thickening and dark pigmentation of the skin. The white arrow points to mild hair loss, hyperpigmentation, and lichenification in a Yorkie.

 


Acute Moist Dermatitis

Commonly know as a hot spot, it is an area of skin that has been maimed from intense pruritis. Pyoderma is also present, and the skin is very painful. Hot spots occur rapidly and can encompass a large section of skin in a short time. Affected areas usually include the rump and the side of the face. Other common causes of hot spots include anal gland problems, ectoparasites like mange, grooming, and deep skin infections. Golden and Labrador retrievers, St. Bernards, Collies, and German shepherds are more prone than other breeds.

The serum that is exuded from the inflamed skin matts the hair and causes the problem to progress under the hair coat without anyone realizing how serious it is. These pets can be so painful tha that we need to sedate them prior to clipping the hair and cleaning the wound.

 


Hot spots can progress and cause serious skin conditions. This is painful and requires immediate care.

 


Otitis externa

This is an infection of the outer ear canal. Sometimes this is the only symptom of allergy, especially food allergies. This ear is so severely infected that it is difficult to ascertain the normal anatomy. The ear canal is completely occluded, necessitating surgery to correct it. This dog is painful.

 


Pododermatitis

Infection of the feet can occur from chronic licking.

 


Acral Lick Dermatitis

These are commonly known as lick granulomas. There are many causes, allergies being a primary one. Other causes include arthritis, skin tumors, inflamed nerves, fungal infections, ectoparasites, and psychological factors like boredom and stress. Once the licking starts the problem is difficult to control. In some cases we have found that the use of the laser has been a significant help.

This small lick granuloma is on the front leg of a Golden Retriever

 


Fleas or flea dirt

Flea dirt is literally droppings from the flea after is has bitten a pet and the blood has passed through the flea’s digestive tract. It looks like pepper, and is easily visualized on a pet with a white hair coat.

This is an example of lots of flea dirt.


Flea eggs are small white particles, similar in size to flea dirt, that fleas lay in a pet’s hair coat. They eventually drop off and contaminate the environment. A pet can have fleas, yet show no evidence of fleas, flea dirt, or flea eggs.

Flea allergy dermatitis typically does not cause hair loss around the face, eyes, and ears like in atopy, although this is not a hard and fast rule.


4. Diagnostic Tests

Diagnostic tests are important even if we strongly suspect an allergy. In some situations other skin diseases can occur simultaneously with the allergy. It is impossible to make a diagnosis in any skin condition just by looking at it. This is because there are many diseases that affect the skin, yet the skin has only a limited number of ways to exhibit signs of disease.

Skin Scraping

It is important to do a skin scraping in many cases of allergy because the lesions of atopy commonly mimic those of other diseases. Ectoparasites like demodex or scabies can cause skin lesions and itching.

Fungal Tests

Ringworm can mimic allergy symptoms. Lesions from Ringworm tend not to be as pruritic as allergies.

Malassezia, another fungus, is commonly associated as a secondary problem when the skin is infected. Even though it is a normal part of an animals hair coat, it will add to the itching if other conditions are present. Common areas for Malassezia include the ears, lips, muzzle, between the toes, and the anal area. Indications that Malassezia is present include pruritis, erythema, and greasy skin with an offensive odor. These symptoms can occur with other diseases besides Malassezia.

Malassezia is diagnosed by the above symptoms and by looking for the organism under the microscope after swabbing the skin and placing the discharge on a microscope slide. Many pets respond to shampooing with specific antifungal shampoos twice weekly. These topicals will only work when the underlying allergy and its associated skin infection are under control. In some cases we use oral antifungal medications to control the problem.

Thyroid Test

Hypothyroidism can cause skin conditions, although dogs with only hypothyroidism are not terribly pruritic.

Fecal Exam

Hypersensitivity to internal parasites can cause symptoms similar to atopy. This is not a common situation.

Skin Biopsy

In some cases it is difficult to make a diagnosis. When we are presented with this situation we will biopsy several small pieces of infected skin and have them analyzed by a veterinarian that specializes in tissue analysis of the skin.

Here is a typical report from one of them. All of the big words mean that in this skin biopsy an allergy is most likely, but autoimmune disease cannot be ruled out for sure.

 


Allergy Testing

Allergy tests are performed in cases where we already have a diagnosis of allergy. The main purpose of allergy testing is to find exactly what your pet is allergic to, and also to set up a protocol for allergy injections. If giving allergy shots is not contemplated then this test is of less value, although it will let us know what allergens we want to avoid. Trying to avoid these allergens though is the hard part because they are in our houses and almost everywhere outside.

There are two main types of allergy tests that are performed. Neither one is perfect, and they can have false positives and false negatives.

Intradermal (skin) Test

Most of us are familiar with the first one. In this test, called the allergy skin test or intradermal test, small amounts of materials that routinely cause allergies in dogs are injected under the skin. The reaction, if any, is graded, and a determination is made as to whether or not a pet is allergic to that specific allergen.

This test is very subjective, and therefore prone to errors in interpretation, and therefore requires significant experience. Many different techniques are used.

Your pet must be off of oral cortisone medication for at least 1 month before testing. If injectable cortisone is given, the waiting time is longer. Your pet must not be on any tranquilizers at the time of testing and must be off of any antihistamine medication for 10 days.

Pets usually are given a sedative to calm them and to minimize the release of cortisone due to stress, which will affect the outcome. The hair on the side is clipped where there is no current dermatitis occurring. A tiny amount of histamine is injected first. If there is no reaction to histamine, the full test is postponed. A small amount of sterile saline is also injected as a control.

The areas where the allergen is injected are marked


Numerous allergens are injected into the skin and a reaction is noted at 15 minutes and again at 30 minutes. The reaction we are looking for is called a wheal. A positive test to a specific allergen occurs when the reaction is in between the saline and histamine tests in size.

In some cases the wheal is obvious, in others it is subtle, which is part of the interpretation process.


RAST (in vitro test)

The second type of test that is performed is called the RAST test. RAST stands for radioallergosorbent test. Another in vitro test is called the ELISA (enzyme linked immunosorbant assay) test. RAST tests for the levels of allergen specific IgE. In this test a blood sample is taken and submitted to a special lab for analysis.

The RAST test has advantages over the intradermal test. There is no clipping, sedating, and there is no potential to have an adverse reaction to an allergen injected into the skin. There is less of a chance that prior drug therapy (cortisone) will influence the outcome, and it can be used in patients that have dermatitis.

The primary disadvantage is the fact that false positives are more common when compared to the intradermal test.

 


The RAST test is very thorough and checks for many different allergens in the home, outside, and in your pet’s food. Here is an example of one of their reports:

Here are 4 of the dozen household allergens they tested. This dog is borderline for orris root and human epithelial cells, and positive for jute/sissal and tobacco smoke.

 


These are a few of the food allergens tested in this sample. There was no allergy to venison, eggs, or milk, but this dog was allergic to soybean.

 


This is a tiny sample of the numerous allergens found in the environment tested for on the same dog as above.

 


Allergy tests can be unreliable at diagnosing food allergy. A better way to diagnose food allergies is using a technique called the elimination trial. By taking away a food that is suspected of causing the food allergy you can determine if the problem resolves. This might take up to several months to know for sure. To verify the diagnosis you need to feed the suspected food again to see if the skin condition returns. Commercial diets that contain rice, venison, fish, and potato are commonly used for the elimination trial. There is a food manufactured by Hills called Z/D that has been a big help in diagnosing and treating food allergies.


Routine Blood Panels

On occasion a specific type of white blood cell, called an eosinophil, is elevated in allergic conditions. Other conditions, notably worms, can also cause this elevation in eosinophils.

A routine blood panel can also give an indication of internal or hormonal problems that might show up as a skin condition. The most important of these are hypothyroidism and Cushing’s Disease.

This blood panel shows an elevated alkaline phosphatase level. This could be an indication of a hormonal problem called Cushing’s Disease.

 


Treatment

In the early years of atopy the pruritis is more easily controlled. As the problem progresses treatment is not as rewarding. Chronic changes to the skin can occur, especially lichenification and hyperpigmentation.

Treatment is aimed at all the factors that contribute to pruritis. For example, a pet that is normally not atopic might become so if exposed to fleas or if it gets a pyoderma. This concept is called summation of effects, and might push the pet over what is called the pruritic threshold.

Avoidance

Obviously, if it is exposure to an allergen that causes the problem in the first place, then logic will dictate that we eliminate this exposure. In reality though, these allergens are everywhere. Minimizing exposure can be beneficial since it will decrease the allergen load, and hopefully keep your pet under the pruritic threshold.

Pets that are allergic to kapok, wool, cotton, feathers, animal dander, newspaper, and tobacco smoke all might benefit from limiting exposure. Limiting the number of houseplants could be helpful, and use synthetic material for your pets bedding. Pets allergic to house dust mites might do better kept out of bedrooms or placed outside more often. Being outside though might expose them to more pollens. Keep the grass cut short, and keep pets out of the yard when cutting the grass. Rinse your pet’s feet and face off thoroughly after being outside can be beneficial in some cases.

Mold allergies might be helped by dusting and cleaning more thoroughly, especially house plants and bathroom carpets. Even think about replacing your carpets with wooden flooring. Keep your pet away from damp areas like basements (in California that’s easy since we don’t have many) and use humidifiers and air conditioners in humid weather. Rinse their filters frequently and clean with chlorine bleach. To truly filter most of the dust, mites, pollens, bacteria, and molds in your house you need to use a HEPA (high efficiency particulate air) filter. Upright vacuum cleaners return most of the dust back into the air, so use canister or cylindric type machines.

Routine and thorough washing, cleaning, and vacuuming of your household will keep mold, house dust, and house dust mites to a minimum. Keep your pet out of the house when doing thorough cleaning and vacuuming to minimize allergens that are stirred up by the cleaning. Put plastic over bedding that might harbor house dust. Keep pets indoors at dusk and early morning during heavy pollen seasons.

Rinse your pets muzzle and feet off with plain water after being exposed to grass and before you bring it in the house.

Flea Control

Since we live in a flea endemic area year round, we cannot emphasize the importance of proper flea control in any pet that has a skin condition. Even pets that are 100% indoors are possible flea victims.

The products available today are a significant improvement over flea control products in the recent past. They are economical, safe, effective, and very convenient. The main products we recommend are Trifexis© and Revolution©. Please ask one of our receptionists for detailed brochures on each to explain how they work, .

There is a new product that will be of significant help in outdoor dogs and cats. It is called Revolution©. In addition to treating fleas, it treats heartworm, ear mites, and internal parasites (depending on the species). This is a huge spectrum of control, and will probably become the future standard. We also have detailed brochures on this product.

Anti-inflammatories

Cortisone

One of the mainstays of therapy for treating atopy is cortisone, commonly know as steroids. These steroids fit in the class of drugs called corticosteroids, which are not the same thing as anabolic steroids used by bodybuilders. Cortisone use is usually reserved for flare-ups, since long term use has the potential for causing side effects. Long term use of high doses of cortisone can lead to hair loss, thinning of the skin, liver problems, stomach problems, and muscle weakness. The overuse of cortisone can also cause iatrogenic Cushing’s disease.

Cortisone is a very potent drug used in human and veterinary medicine literally thousands of times each day. Without this drug we would not be able to treat a large number of diseases. Cortisone has been abused by some people, leading to a bad name for this drug in some people’s minds. When used judiciously, and under a doctor’s supervision, it is one of the most important drugs we have. It is our first line of defense when a pet is scratching so severly it is maiming itself.

Cats are more resistant to the side effects of cortisone than dogs. Some cats are difficult to pill, so it is not uncommon to use an injectable version of cortisone that lasts for several  weeks to months. Older cats need to be checked for underlying problems like sugar diabetes and heart disease before instituting cortisone therapy. Cortisone will raise the blood sugar level, making it more difficult to control the problem. It can also cause the body to retain more sodium. This is only a problem in a cat that is in congestive heart failure.

Cortisone is usually given on an every other day basis. This minimizes side effects yet still gives an adequate amount of the drug to minimize scratching. In many cases we give an injection first to give your pet immediate relief from the scratching. We routinely use cortisone for 1-2 weeks to help get the scratching problem under control. Since cats are more tolerant to cortisone, and can be difficult to pill, it is not unusual to use the injectable version of cortisone in them.

While on cortisone you will notice that your pet drinks and urinates more than usual. It might also have an increased appetite and might show some behavioral changes. These symptoms will go away, in the meantime make sure your pet has access to fresh water at all times and can go outside to use the bathroom frequently.

Antihistamines

Antihistamines can be effective in treatment in some cases. They counteract the release of histamine (that’s why they are called antihistamines) from the mast cell, which as you know is the source of the itching. They are the mainstay of our long term medical treatment for skin allergies. Occasional side effects include drowsiness and dry mouth, both of which tend to resolve. In general, they are safe to use on a long term basis.

We will initiate an antihistamine trial to determine which one, if any, is most effective for your pet. We do a trial for up to 2 weeks to determine if one is effective or not. It is helpful not to have your pet on cortisone at the same time we are trying a new antihistamine, since we will not know if a decrease in pruritis is due the cortisone or the antihistamine. If we find one antihistamine that works well we stay with it on a long term basis. Eventually this might change, and if there is a significant flare up we will use cortisone to control the problem for several weeks. In the long run, even if antihistamine use has only minimal effects on decreasing pruritis, its use can help us decrease the use of cortisone.

Some of the common antihistamines we use are:

  • Benadryl A
  • Atarax
  • Tavist
  • Chlorphenaramine
  • Amitryptiline
  • Temaril- P  This is an antihistamine/cortisone combination that uses small doses of each drug with a synergistic effect.

Medications used to treat allergic dermatitis are used on a long term basis. We will refill medications as needed, and require a complete physical exam every 6 months to verify we are still treating the correct problem and to check for potential side effects to medication. A blood sample will be recommended periodically to verify the health of internal organs that might be affected by long term medication.

Apoquel

This new medication from Zoetis (the old Pfizer) has proven to be highly effective at controlling this problem. Zoetis has a major backlog on this effective product and is giving it out in only limited quantities.

Antibiotics

Some dogs scratch so severely they cause a secondary bacterial infection of the skin called pyoderma. The bacteria that commonly causes this is called Staphylococcus pseudo intermedius. This secondary bacterial infection intensifies the itching. These dogs need treatment with antibiotics for several weeks to several months. In addition, they need to be bathed with shampoo that will help the skin infection. Long term use of antihistamines are not effective if a skin infection (pyoderma) is allowed to persist.

If a hot spot is present it will be gently clipped and cleansed. Pets with hot spots must be put on antibiotics and usually short term cortisone to prevent the problem from progressing. Hot spots are very painful, and oftentimes require sedation if the wound is to be clipped and cleansed properly.

Antibiotics that work best for pyoderma include:

  • Cephalexin
  • Baytril
  • Clavamox

There is a new version of injectible antibiotic called Convenia that lasts for 2 weeks. This is especially useful in cats due to the difficulty in giving them a pill.

Antifungals

Secondary fungal infections can occur, especially when the feet are licked constantly. The most common one is called Malassezia. It is treated with topical antifungals in most cases.

Cyclosporines

Another treatment for atopy relies on cyclosporines, the medication that prevents organ transplant rejections. It is called Atopica©

Atopica© is used to replace cortisone in dogs only. Your dog must weigh at least 4 pounds for it to be used. Its main advantage is the fact it works without any side effects on a long term basis that can be encountered in drugs like cortisone.

It can be highly effective, but might cause vomiting and diarrhea, which might resolve on its own after a period of time. Initially it is given once daily for 30 days, and should be given one hour prior or two hours after a meal. If a response is achieved we will decrease the dose slowly, with the ultimate goal of giving it twice per week. It becomes cost effective at this twice per week dosing, and it is probably warranted to try this medication if your dog is on chronic cortisone use.

Allergy Shots

If an allergy test is performed on your pet we will know what it is allergic to, and allergy shots can be custom designed for your pets specific allergy. Giving allergy shots is called hyposensitization or immunotherapy. Theoretically, hyposensitization stimulates the production of IgG, which subsequently attaches to the allergen, preventing IgE from attaching to this same allergen. If there is no IgE attached to the allergen, then the mast cells do not release histamine.

Even if you do not give the allergy shots, knowing what your pet is allergic to can be beneficial in some cases, assuming you can remove the offending allergen (see previous section on avoidance). We tend to rely on allergy shots when avoidance methods and medication are unsatisfactory in minimizing pruritis.The company that performs the RAST test also supplies us with the allergens to give the allergy shots.

Giving allergy shots can be a significant way to minimize your pets scratching, although just like in people, no guarantee can be given to the outcome. Estimates vary, but in general, you can expect some improvement 60% of the time. In some cases we will still keep your pet on an antihistamine or cortisone, or Atopica©, but at a reduced dose. A decision to undertake this treatment modality takes a commitment to a lifetime of giving these injections in most cases.

Giving the injection is very easy since it is a small amount with a tiny needle. We will teach you how to give them, and if need be, will give them for you. Initially, the injections are given every few days for several months. It takes at least several months to know if the injections are working, and up to a year for full effectiveness. Eventually, they are only given from once every few weeks to only a few times per year. Each pet’s response is different.

Allergens are made specifically for each pet. This dog is allergic to many things, so three vials are needed to treat its problem.

 


Food Allergy

Hypoallergenic means foods that your pet has never eaten, which technically, it cannot be allergic to. Even though food allergies are not a common cause of skin conditions in dogs, we recommend using these foods in some cases when we feel the pruritic threshold has been reached and any decrease in allergen load will put your put under this threshold. It might take up to 2 months to know if the food is working. You cannot feed any other foods or treats during this trial period, so plan on rewarding your pet with something else besides food.

Hypo allergenic foods that contain fish, lamb, potato, or venison used to be the most effective. We now recommend Hills Z/D© or D/D© as the most effective treatment for food allergy. We have detailed technical information on these foods to review with you if one of our doctors feels they are appropriate.They are unconditionally guaranteed and you will get your money back if you are not satisfied.

It is important that you do not have your pet on cortisone or antihistamines while trying to determine if your pet has a food allergy, since they will decrease the scratching and lead to an erroneous conclusion on the effect of the food. This causes a dilemma for those pets that have significant scratching, since they need immediate relief. In these cases we recommend using medication initially and starting your pet on a hypo-allergenic diet at the same time. If the itching is decreased after 1-2 months you can start weaning your pet off the medication to determine if the scratching is still diminished while on the hypo-allergenic diet also. In some cases we find the use of this food will allow us to use less medication to control the scratching.

Room Purifier

If your pet is kept in a confined area, the use of a room purifier that filters out pollen particles can be of help.

Food Supplements

Some allergic dogs and cats scratch less when supplemented with essential fatty acids. The main ones we use are Derm Caps and EFA-Z. As with other therapeutic options, essential fatty acids will not work when the skin has pyoderma. It will take at least several weeks of supplementation to see any improvement. In some cases the need for inflammatory medication will be reduced when a pet is put on essential fatty acids supplementation.

 


Bathing

Bathing in cool water several times per week is beneficial. Do not use hot water because it can intensify the itching. Proper bathing will help remove allergens and eliminate dry skin, both factors that affect the pruritic threshold. Bathing your pet too often will dry its skin out and increase its itchiness.

We have many different shampoos that will help you- please ask one of our receptionists to show you. We have had best results with oatmeal shampoos and rinses, along with antihistamine shampoos and rinses. Use a mild shampoo once weekly to keep the hair coat clean without drying it out. For hot spots we use Oxydex shampoo. If we suspect a secondary fungal infection caused by Malassezia we will use an antifungal shampoo called chlorhexidine.

This is an allergic reaction to shampoo in the arm pit area of a 8 month old female pit bull named Pumpernickel. This illustrates the principal that many things can cause an allergic reaction, even treatments for allergies.

 


Topical Medications

There is a strong tendency on the part of pet owners to use topical medications for allergic skin disease. They are used, and are helpful, but should not be relied upon as the primary source of treatment. Topical medications we use usually have an antibiotic, an antihistamine, or cortisone as ingredients. We tend to use topical agents most often when presented with pets with hot spots. In these cases we use antibacterial creme in addition to antibiotics that are given orally.

 


Prognosis

Allergic Dermatitis is a chronic disease that is not cured, only controlled. It can be the cause of significant frustration, and will wax and wane in some cases. Understanding this disease will help you formulate a long term plan that suits your needs and minimize the chance of side effects when medications are used on a long term basis.

Our online store can provide you with pet products and prescriptions mentioned above. We are competitive with any online organization, along with the added convenience of pre-approval by our doctors and products that are safe and effective, backed by the manufacturer’s guarantee.

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