How Can the Veterinary Nurse Assist in the Treatment of the Allergic Patient?
World Small Animal Veterinary Association World Congress Proceedings, 2014
Valerie A. Fadok, DVM, PhD, DACVD
North Houston Veterinary Specialists, Spring, TX, USA

Chronic inflammatory diseases are difficult for clients, and managing their pets' allergic skin diseases is no exception. It is very important that everyone on the veterinary team support the clients in their efforts. It has been shown recently that allergic skin disease has significant impact on quality of life, not only for the patient but for the owners too. Veterinary nurses are invaluable in providing clients with allergic pets the proper information and support, so that they understand the disease process and why we recommend the diagnostic tests and treatments we do.

The three major allergies we see in dogs and cats are flea allergy dermatitis, atopic dermatitis/atopy, and food allergies. Animals may have one, two, or all three of these problems! Understanding the pathogenesis allows the veterinary nurse to explain the disease to owners, and to help set realistic expectations. Most importantly, owners need to understand that allergic diseases are not curable.

Flea Allergy Dermatitis

Flea allergy is the most common skin allergy we see in dogs and cats. We have learned much about the flea life cycle and how to break it, and we have a plethora of products, yet many clients still struggle with fleas. Most failure of flea control is not related to product failure; it is related to unrealistic client expectations and misuse of their flea control products. Client education about the flea cycle and how products work is an area in which the veterinary nurse shines. Furthermore, flea control works best when we understand the client-pet relationship, what they do together, and what products will work best for them. Then we can make a recommendation specifically for that family, and get better results.

Here is what clients need to know about flea allergy:

1.  In dogs, flea allergy often presents as itch and hair loss on the caudodorsal back, but lesion can be more extensive. Secondary pyoderma is common. In cats, we can see aggressive self-grooming, military dermatitis, and eosinophilic granuloma, particularly eosinophilic plaque.

2.  When pets have flea allergy, fleas and flea dirt can be difficult to find, because allergic animals groom extensively and remove the evidence.

3.  Indoor cats and dogs can get fleas. We can carry them into our homes on our clothing.

4.  Flea allergic pets require very few fleas to become itchy, and the itch from an infestation can last several days.

5.  The best way to treat flea allergy is to utilize excellent flea control every 30 days throughout the year.

Great resources can be found on the website of Dr. Michaal Dryden (Dr. Flea). There is a link to an excellent video you can share with clients: The Dirt on Fleas. (

Is resistance developing to our flea control products? It is possible but when flea control appears to be failing we need to consider other factors.

These are the most common reasons for flea control failure:

1.  The product is not being used every 30 days throughout the year.

2.  The product is not be used for all dogs and cats in the household.

3.  The topical product is not being applied directly to the skin, or the spinosad is not being given with a full meal.

4.  An application meant for one animal is being shared among animals.

5.  Pets are exposed to fleas brought into our yards by wildlife or feral cats and dogs.

6.  Pets are exposed to fleas seeding dog parks, boarding kennels, and other places dogs and cats congregate.

7.  Unrealistic or mistaken expectations. If owners have not been using their flea control regularly, the home and yard environment have become infiltrated by eggs, larvae, and pupae. When they resume their flea control, it will take 8–12 weeks before the flea population will be eradicated. Furthermore, no product has 100% efficacy, so a few fleas will slip through. For best results, owners should use an adulticide that kills fleas so quickly they can't lay eggs, or they should use a product that combines adulticide activity with an ability to inhibit development of larvae. For owners that want quick results, environmental extermination can be very helpful. Professional pest control operators can spray with a safe adulticide and an insect growth regulator.

Treating flea allergy requires good flea control, and we would like to use a product that kills fleas quickly and/or has repellency. The latter is usually provided by permethrin which is only safe to use on dogs. Oral flea control medications have been shown to be effective in dogs and cats with flea allergy. One of them, nitenpyram (Capstar) can be used as a diagnostic test: it is given every other day for one month. If all the itch goes away, flea allergy is the cause of the skin disease, and we can then select the appropriate product. Some dogs may require bathing and antibiotics for associated pyodermas, and medications (glucocorticoids, oclacitinib) to control itch at least initially. The major concept to emphasize to owners is that the cause of itch is fleas, and that flea control is the best way to control itch.

Four quadrant flea control is a concept that can help us decide what products will work best for individual client/pet combinations. You can fill in the boxes with the products you have available and show these to clients to help them get their fleas under control quickly.


Atopic Dermatitis/Atopy

We have learned a lot about this disease in dogs in the last 10 years; we know much less about it in cats. Atopy is an inherited predisposition to develop allergic reactions to environmental allergens including pollens, molds, dusts, danders, mites, and foods. We call the skin disease atopic dermatitis in dogs because we know it is very similar to the disease in people, and part of the pathogenesis is a skin barrier defect. The skin barrier consists of the surface cells in the stratum corneum sitting in a sea of lipid (ceramide, cholesterol, fatty acids). When it is normal it keeps the allergenic proteins out. But when it is defective, the allergens can be absorbed more deeply into the skin where the immune system can reach them. The immune system is skewed toward a T helper 2 response, and this results in the production of a number of cytokines which mediate itch and inflammation. It also makes dogs more prone to bacterial and yeast skin infections because they can't kill these organisms, and they can become allergic to the Staphylococcus and Malassezia too. The severity of the disease is determined by the genetic background and the environment. Some dogs will be mildly affected in areas where pollination is limited; if these dogs move to an area in which pollination is year-round, their disease is more severe. We know less about this disease in cats, but we do know that cats react to environmental allergens and that we can use immunotherapy to help reduce their symptoms.

Here is what your and the client need to know about environmental allergies:

1.  Dogs with atopic dermatitis are face rubbers, foot lickers, and axilla scratchers. Areas most severely affected are those sparsely haired. These areas are where dogs most readily absorb allergens through their abnormal skin. Cats show the syndromes of over grooming, miliary dermatitis, and eosinophilic plaque when they have environmental allergies.

2.  Atopic dermatitis is a lifelong disease. These animals will require treatment for their entire lives because we can't cure this disease. Our goal is to try to identify them when young, and get them on the path to recovery to prevent recurrent bacterial and yeast infections, chronic skin changes and intractable itch.

3.  The only treatment that can change the abnormal immune response is immunotherapy. If we can allergy test these animals when young, and get them started on immunotherapy (either injection or sublingual drops) early, we have an excellent chance of reducing dependency on drugs that mask itch.

4.  If immunotherapy is not used, animals will require medication for the rest of their lives. Medications used include glucocorticoids, cyclosporine, and oclacitinib.

To get control of this disease, we recommend a multimodal approach:

1.  Avoid any allergens that you can. Practically speaking, we can avoid food triggers and fleas. But owners can use bathing and wipe-downs to reduce pollens on the skin, and they can control house dust mites in the home.

2.  Use immunotherapy to change the abnormal immune response. We have learned that immunotherapy based on serum testing is as effective as that based on intradermal testing. Traditionally subcutaneous injections have been used for immunotherapy. Some owners are not comfortable with giving injections. We now can offer sublingual immunotherapy (allergy drops) for those clients uncomfortable with giving their dogs injections.

3.  Control infections by using bathing and when necessary, antibiotics and antifungal drugs.

4.  Repair the skin barrier by feeding optimal nutrition, by using oral fatty acids, and by using topical lipids in shampoos, sprays, and/or spot-ons.

5.  Control itch! This may require glucocorticoids, cyclosporine, or oclacitinib.

If clients understand that the disease is manageable but not curable, they will have realistic expectations and over time, they can develop a program that allows them to have a comfortable life with their pets.

Food Allergy

Food allergy in dogs and cats is not well understood, but we do know that some itchy pets respond to dietary manipulations. Food allergy in dogs can be part of atopic dermatitis; some dogs with pure food allergy will resemble dogs with flea allergy. Recurrent otitis externa has also been associated with food allergy in dogs. In cats, we see the feline triad of over grooming, miliary dermatitis, and eosinophilic granuloma complex. We also see intense head and neck itch. Owners have many misconceptions about food allergies which we need to dispel.

Here are some common misconceptions about food allergy:

1.  A change in diet precedes food allergy. Most animals that develop food allergy have been eating the protein for a long time. It takes a lot to break the tolerance that the gut immune system sets up for foods.

2.  Feeding a hypoallergenic diet has a dominant effect. Some clients believe that if they feed the hypoallergenic diet, it will negate the effects of table scraps and treats. When we feed a hypoallergenic diet, we must cut out all of the foods that an animal has eaten. We may need to be creative about substitutes during the diet trial.

3.  Certain foods are naturally hypoallergenic. There is no one hypoallergenic protein or carbohydrate that meets every animal's needs. Animals can become allergic to any protein that is a regular component in their diet.

4.  Grain-free diets are hypoallergenic. Grain-free diets have become very popular due to misadvertising by some members of the pet food industry. Grain-free diets will only be hypoallergenic if pets are allergic to grains, and grain allergies are not common.

5.  Food allergy is not steroid responsive. While food allergic pets may need more steroid to control their itch, steroids often do provide relief and can be used as we initiate the food trial.

6.  Serum allergy testing will be able to help a client pick safe foods. This is not true. Positive serum tests may help us determine what foods to avoid, but negative tests do not tell us what foods are safe.

The gold standard for diagnosing food allergy is a diet trial that reduces the itch and clinical signs and then food challenges to verify the offending food. There are several choices, but if a commercial product is used we recommend prescription diets. We have learned that the over-the-counter limited ingredient diets can contain trace contaminants of chicken, beef, soy, or grains, as they are not produced under the same stringent conditions. My preference is to use a novel protein diet, but these are becoming more difficult to find in prescription diets. We can consider hydrolyzed diets, but it is important to know that not all allergic patients will do well with hydrolyzed proteins, as their immune system can still react to the hydrolyzed protein. Sometimes the best diet is a home-cooked diet, containing novel protein and carbohydrate sources, and balanced by a nutritionist.

Here is my approach to a food trial:

1.  I get as detailed a food history as I can. I assure the owner that the prescription diet or home-cooked diet is a diagnostic test; it is not the permanent diet. By setting a time limit, we encourage better compliance. I assure each client that I will do my best to get their pet back onto a commercial diet.

2.  I recommend feeding the test diet for 6–8 weeks. In that time, we should see at least some improvement if food allergy is the cause of the signs.

3.  If the itch and skin disease improve with the diet, we will do food challenges.

4.  The first food challenge is to feed the old diet. Small amounts are mixed into the test diet over a week. If itch occurs, then we are convinced food allergy is the problem and we can move on to single food challenges. If there is no increase in itch after two weeks, then likely the diet was not the problem; environmental allergens are more likely.

5.  Single food challenges are done by adding small amounts of the single ingredient to the diet every 1–2 weeks. When itch flares up, we remove it and give the animal time to settle down. Then we can move onto the next ingredient.

6.  After 6–8 weeks, the owner should have developed a list of foods tolerated and foods not tolerated. They can then look for appropriate over-the-counter diets.

7.  We commonly challenge with chicken, beef, lamb, pork, turkey, fish, wheat, corn, soy, dairy products.

Useful References

1.  Bryan J, Frank LA. Food allergy in the cat: a diagnosis by elimination. J Feline Med Surg. 2010;12(11):861–866.

2.  Dryden MW, Carithers D, Murray MJ. Flea control: real homes, real problems, real answers, real lessons: fleas in a flash! Compend Contin Educ Vet. 2011;33(4):E5.

3.  Dryden MW, Carithers D, Murray MJ. Flea control: real homes, real problems, real answers, real lessons: where are all these fleas coming from? Compend Contin Educ Vet. 2011;33(5):1, preceding E1–7, quiz E8.

4.  Dryden MW, Carithers D, Murray MJ. Flea control: real homes, real problems, real answers, real lessons: the "deep dive." Compend Contin Educ Vet. 2011;33(7):1, following E1–8.

5.  Gaschen FP, Merchant SR. Adverse food reactions in dogs and cats. Vet Clin North Am Small Anim Pract. 2011;41(2):361–379.

6.  Halos L, Beugnet F, Cardoso L, Farkas R, Franc M, Guillot J, et al. Flea control failure? Myths and realities. Trends Parasitol. 2014;30(5):228–233.

7.  Mandigers P, German AJ. Dietary hypersensitivity in cats and dogs. Tijdschr Diergeneeskd. 2010;135(19):706–710.

8.  Marsella R, Olivry T, Carlotti DN. International Task Force on Canine Atopic Dermatitis. Current evidence of skin barrier dysfunction in human and canine atopic dermatitis. Vet Dermatol. 2011;22(3):239–248.

9.  Nuttall T, Uri M, Halliwell R. Canine atopic dermatitis - what have we learned? Vet Rec. 2013;172(8):201–207.

10.  Olivry T, DeBoer DJ, Favrot C, Jackson HA, Mueller RS, Nuttall T, et al. Treatment of canine atopic dermatitis: 2010 clinical practice guidelines from the International Task Force on Canine Atopic Dermatitis. Vet Dermatol. 2010;21(3):233–248.

11.  Siak M, Burrows M. Flea control in cats: New concepts and the current armoury. J Feline Med Surg. 2013;15(1):31–40.


References are available by emailing


Speaker Information
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Valerie A. Fadok, DVM, PhD, DACVD
North Houston Veterinary Specialists
Spring, TX, USA

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