Itchy Dogs: Pollens Barely Scratch the Surface

A very common problem we see here is some form of chronic or recurrent itching. The cause most often suspected by the owner is fleas; but we find that this is not nearly so often the case, especially with all of the effective products on the market for flea control.

The most common cause of itching in dogs in this area is usually allergy (atopic) related. The most common cause of itchy ears and ear infections in the dog is allergies, whether they are inhalant/environmental or food related. The main places dogs with allergies seem to itch is the feet, face, and ears; with the tail head, trunk, limbs, ears, axillary ("armpit"), inguinal ("groin") and perineal (genital/anal) areas being close seconds.

WHAT IS AN "ALLERGY"?

The most common type of allergic reaction people see in their dogs (and in themselves) is a Type I Hypersensitivity (there are 4 Types, but for the scope of this writing, only Type I will be addressed). Allergies are basically the immune system overacting or acting inappropriately. When the body is exposed to a foreign protein like is found in a virus or bacteria, it usually makes an antibody called IgG to neutralize that foreign protein. In some animals and people, the body makes IgE instead of IgG and that is where the problem begins.

In the typical allergic reaction, a reactive chemical called histamine is released from granules in a cell called a mast cell. The mast cells are stimulated to release this chemical by a protein (which is actually a type of antibody) called IgE. IgE is specific for certain allergens (which are foreign proteins found in pollens, foods, molds, etc.). When the body is exposed to certain levels of specific allergens, it responds by releasing IgE specific for that allergen. The IgE then stimulates the mast cells. The mast cells in turn release histamine ("degranulate") which causes the inflammatory reactions seen in common allergies. In people, the offending chemical IgE, is in highest concentrations in the respiratory tract and mucous membranes (eyes, nose, mouth), but in dogs the concentration is much higher in the skin. This is why people more often have "hay fever" symptoms and dogs get itchy skin more often.

An allergy is technically an immune response, therefore it requires previous exposure. This means a patient will usually not have a reaction the first time they are exposed to an allergen because the body needs time to react and make IgE. Also, in regards to food based allergies, it is possible to develop a food allergy to a food source which the patient has been eating for years. Allergies also can change with age, so the results of one test may not be the same years later as new allergies can develop with time.

  WHAT IS THE PRURITIC THRESHOLD?

The idea of the pruritic ("itchy") threshold is that there is for every animal (or person) a level or amount of allergens (allergy inducing particles) that must be present before symptoms (itching, etc.) will occur. Every animal has a different threshold. An animal can be allergic to something in their food all year long and never show symptoms as there is not enough allergen exposure to cross the threshold; however, if they are also allergic to ragweed, then when ragweed season is in full force, they are itchy because the food allergy and the ragweed allergy when added together cross the threshold. If we are able to determine the food component and remove that food, then there is a chance that the ragweed season will not affect that pet because the threshold is no longer being crossed.

Another way to look at it is as follows: Let's assume that Jake the Labrador has a pruritic threshold of 6 (numbers strictly for illustrative purposes). Let's now assume for Jake that beef counts as a 2, wheat as a 3, and Bermuda grass as a 3. If he is eating a diet that has beef and wheat in it and he lives in a Bermuda grass dominated area (like North Texas), then his body is experiencing an allergen exposure level of 8, which is above his threshold of 6. This means he will most likely show some level of symptom all year. This may manifest in the skin or maybe only in the ears as an infection that is never totally cleared. Since we cannot remove the Bermuda grass from the environment, we can try him on desensitization injections (these are explained later) to reduce the effect of the Bermuda grass which may put him at an allergen exposure level of 5 which is below his threshold. Alternately, if we change his diet to something with different meat and starch sources (e.g. duck and potato) and if his numbers for these two food sources are 1 each, then he is at a level of 5, which is below his threshold even without doing anything about the Bermuda grass.

 WHAT DOES IMPAIRED SKIN BARRIER FUNCTION MEAN?

Another component of skin allergy is related to the skin barrier. This barrier is actually a physical barrier. In allergic dogs, there is often an impairment of this barrier which allows pollens and other allergens to physically penetrate the skin deeply and stimulate the allergic response from their mere presence. This is why dogs with grass allergies often seem to have a problem primarily with their feet and that often there is some level of relief offered by covering the feet before allowing walking on the grass and/or from wiping the feet down shortly after coming inside from the grass. The exposure is not a simple inhaling issue like in people, but a physical contact issue with the skin.

WHAT ARE SOME COMMON TREATMENT STRATEGIES FOR ALLERGIES?

Avoidance:

This is the most effective but often least possible treatment choice. If we are able to remove the offending agent from the environment or diet, then there is no stimulation and therefore no reaction. This is most easily done with food allergies by using elimination diets and/or novel protein diets. An elimination diet basically means feeding a diet from which all offending food sources have been eliminated. Novel protein diets simply mean feeding a diet in which there is a novel (new or never seen by the body before) protein source. Quite often the two diets used are one in the same.

The hard part of the food component is that it can take 2-6 months of feeding a strict diet before the body no longer shows reaction to the allergens from the old food. Allergy testing by blood sample may help at least rule out some of the more reactive foods to help streamline the diet selection.

Testing and Immunotherapy:

Allergy testing is the best way to find the source of some allergens to see if there is something that can be removed from the environment or diet, or if there is a specific serum that can be made for the pet in question so that they are not nearly so reactive to that allergen. Once tested, a serum or "vaccine" can be manufactured that is specific for the offending agents for a given patient. The idea behind this is to inject small concentrations of the allergens to teach the body to make IgG instead of IgE. It can take a few months to a year before a patient responds favorably to the injections, and there are cases in which some patients never respond properly. Many people are stopped by the cost of the testing up front, but if they were to add up all financial costs of the exams, tests, pills, injections, and topical medications that they end up buying to treat the chronic skin and ear issues; plus the physical cost to their pets from the chronic inflammation, irritation, discomfort, and infections from the allergies, then testing will almost always pay for itself in the long run. Please remember that allergies also can change with age, so the results of one test may not be the same years later as new allergies can develop with time. If a patient that has been doing well on injections for a period of time develops symptoms again, it is often recommended to retest to be sure a new allergy has not developed. If one has, then the serum for the injections needs to be changed.

Oral Medications:

Antihistamines work well in very few dogs (maybe 15%). They actually fail more often than they work. They do not stop the allergic reaction; rather they work by stopping or slowing the release of the histamines from the mast cells. They are a symptomatic treatment. They usually have very low side effects and can be used on an as needed basis. They tend to be relatively inexpensive. Even those who report some level of improvement with antihistamines may find that they no longer work the next season. Also, there is no way to tell if the antihistamines "working" coincided with some pollen source leaving the environment thus lowering that pet's exposure level making them fall beneath their threshold. This means they would have improved without the antihistamines anyway.

Steroids work very well, but they do not necessarily stop the allergy, but they do decrease the immune system response and the effects of the inflammatory chemicals in the body. They also tend to be relatively inexpensive. Chronic use however can be detrimental to your pet's health. They have many potential side effects including but not limited to: increased thirst, increased urination, increased appetite, weight gain, lowered wound healing, lowered immune response, behavioral changes. They are usually best used in short courses to get immediate results while looking to other long term therapy choices.

Immune regulating agents such as cyclosporine or Atopica^® work by lowering the immune system response and therefore lowering the symptoms. They have fewer side effects than steroids, but tend to be more expensive.

Omega -3 fatty acids are products found in certain foods and in supplements that have no real side effects and can greatly reduce the inflammation in the skin caused by allergies. They can be used in conjunction with any of the other therapies. The best form is eicosopentanoic acid or EPA. Many human products have low EPA but more ALA and DHA. These last 2 are not nearly so effective in the dog as EPA, so it is best to use ones formulated for dogs.

Topical Therapy:

Sometimes pets respond well to topical therapies like sprays and shampoos. The sprays most often have a steroid or antihistamine base, with some having a mild topical anesthetic added. These are usually temporary treatments. Topical steroids if used long enough can also enter the blood stream and start having the same negative effects that oral steroids can have. The shampoos may have benefit from actually physically cleansing the allergens off the skin; from applying anti-inflammatory products; or from treating secondary bacterial and yeast infections.

Get yourself informed and then come in and see if we can help you and your pet get some relief.