Nutritional management of allergic skin disease: a roundtable discussion (Sponsored by Royal Canin)

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A discussion on diagnosing and treating adverse food reactions.

Dr. Reid Garfield: Received his Doctor of Veterinary Medicine degree from Texas A&M University in 1981. He practiced general veterinary medicine in the Dallas area until 1990 when he began a dermatology residency at the Animal Dermatology Referral Clinic. Dr. Garfield became a member of the American Academy of Veterinary Dermatology in 1992 and achieved Diplomate status in the American College of Veterinary Dermatology in 1994. Dr. Garfield currently practices at the Animal Dermatology Referral Clinic in Dallas, Texas.

Dr. Reid Garfield

Dr. Dana Liska: Received her Doctor of Veterinary Medicine from Kansas State University in 1999. Following graduation she completed a rotating internship in medicine, surgery, and critical care at Mission MedVet in Mission, Kansas. Dr. Liska then practiced general, small animal, veterinary medicine for four years in Helena, Montana. In 2004 she began a dermatology residency at the University of Florida College of Veterinary Medicine. Upon completion of her residency she remained at the University of Florida CVM as a clinical instructor of Dermatology until she moved to the Dallas area to join the Animal Dermatology Referral Clinic. She became a member of the American Academy of Veterinary Dermatology in 2001 while in private practice and achieved Diplomate status in the American College of Veterinary Dermatology in 2006. Dr. Liska practices as a veterinary dermatologist at the Animal Dermatology Referral Clinic in Dallas, Texas.

Dr. Dana Liska

Dr. Tim Strauss: Dr. Strauss received his Doctor of Veterinary Medicine degree from the University of Minnesota in 1999. He practiced general veterinary medicine in the St. Paul area of Minnesota for two years before entering his dermatology residency program with Dr. Patrick McKeever in 2001. He became a board certified Diplomate of the American Collage of Veterinary Dermatology in 2004. He returned to his home state of Colorado in 2005 to practice dermatology at the Veterinary Referral Center of Colorado. Doctor Strauss is now the owner of Rocky Mountain Veterinary Dermatology in Frederick, Colorado.

Dr. Tim Strauss

Dr. Valerie Fadok: Staff dermatologist at Gulf Coast Veterinary Specialists, Houston, Texas for three and a half years. Before that, Dr. Fadok was at Veterinary Referral Center of Colorado in Denver. Dr. Valerie Fadok received her Doctor of Veterinary Medicine degree from Washington State University in 1978, after which she completed an internship in small animal medicine and surgery at the West Los Angeles Veterinary Medical Group. A residency in veterinary and comparative dermatology followed at the University of Florida College of Veterinary Medicine, and Dr. Fadok became board certified in veterinary dermatology in 1982. Valerie Fadok has worked on the faculties of University of Tennessee, University of Florida, and Texas A&M. She received her PhD in experimental pathology at University of Colorado Health Sciences in 1991, and has served on the faculty in Department of Pediatrics at National Jewish Medical and Research Center.

Dr. Valerie Fadok

Karen E. Felsted, CPA, MS, DVM, CVPM

Dr. Karen Felsted received a degree in marketing from the University of Texas at Austin. She spent the next twelve years in accounting and business management, including 6 years with Ernst & Young. During this time she earned both her CPA and an MS degree in Management and Administrative Science from the University of Texas at Dallas.

Dr. Karen Felsted

In 1996 Dr. Felsted graduated from the veterinary college at Texas A & M University and practiced both small animal and emergency medicine for three years. For the last ten years she has provided financial and operational consulting services to veterinarians, most recently with Brakke Consulting and Gatto McFerson CPAs.

Dr. Felsted joined the National Commission on Veterinary Economic Issues as Chief Executive Officer in June 2008. She has written an extensive number of articles for a wide range of veterinary publications and speaks regularly at national and international veterinary meetings. She is a founding director and current member of VetPartners, a past member of the Veterinary Economics Editorial Advisory Board, and the current treasurer for the CATalyst Council.

Dr. Karen Felsted: I am Dr. Karen Felsted. I will be the moderator. Today, we are going to discuss diagnosing and treating adverse food reactions. Lef s start by talking about how frequently you all see these kinds of cases.

Dr. Garfield: In food allergic patients, the symptoms are always non-seasonal. About a third of our patients in the Dallas area start out with year-round or perennial symptoms. My guess is that about 20 percent of those with perennial symptoms are food allergic. This would equate to about 6 percent or maybe as high as 10 percent of all the allergic patients we see.

Dr. Liska: I would agree with Dr. Garfield.

Dr. Strauss: I would agree with that for dogs. I think it is a pretty significant difference with cats. I would say food allergies or adverse food reaction in cats represents about 40 percent of pruritic feline patients. I think there is a big difference between the dog and the cat.

Dr. Fadok: I would be willing to wager 10-15 percent of the dogs we see have food allergy or an adverse food reaction. I suspect there is a subset of those dogs that are atopic as well, maybe as much as 50 percent based on some data from Linda Messinger's practice at Veterinary Referral Center of Colorado (VRCC). I would also estimate that 10 percent of our atopic dogs have food allergies too. This can make sorting out the contributions of food compared to environmental allergens quite difficult!

Dr. Felsted: So how do you all go about diagnosing adverse food reactions? What clinical signs make you suspect a food allergy?

Dr. Garfield: Symptoms of food allergy and atopic dermatitis are indistinguishable, although food allergic individuals tend to be more severe than atopic patients. Symptoms are always perennial and tend to be less responsive to symptomatic treatment. When we are trying to control secondary infections and calm itch with antihistamines and even with steroids, food allergic patients tend to not respond as completely or as quickly to those medications.

Dr. Liska: I would agree.

Dr. Strauss: I would just point out that there is very significant overlap in the clinical presentation of food allergic individuals and atopic individuals. There is not any reliable distinguishing clinical sign to differentiate those. You really have to work through the diagnosis to come to the conclusion of a food allergy.

Dr. Felsted: Any difference between dogs and cats?

Dr. Strauss: In canine patients, pruritus, of course, is the main thing that we see. I see erythema in the ears, axillae, feet (interdigitally, palmar and plantar surfaces), around the eyes, ventral abdomen and under the tail. These patients have significant pruritis. With cats the most common presentation is miliary dermatitis.

Dr. Fadok: I see 3 distinct patterns in dogs: itchy ears only, caudal half of the body and an atopic dermatitis-like pattern (foot and axilla chewers, face rubbers, etc). The cats I see tend to exhibit severe head and neck pruritus, generalized itching, or eosinophilic plaques and hair pulling.

Dr.Strauss: I would be interested to hear what the rest of the group thinks about concurrent GI signs. The incidence of concurrent enteric disease with our food allergic patients, I think, is pretty high. Probably about one-third of them have some GI signs in my experience. Would you guys agree with that?

Dr. Liska: The patient may have GI signs at the time of presentation, or if I look back in their medical history they have been a patient with GI disturbances such as intermittent gastroenteritis or perhaps chronic vomiting.

Dr. Fadok: In our practice, I'd say 25-30 percent have GI symptoms, but not major ones. Otherwise Internal Medicine would be seeing them.

Dr. Felsted: Does it help you diagnostically knowing about GI symptoms?

Dr. Garfield: I always felt like the history or presence of concurrent GI symptoms made me suspect food allergy a little bit sooner. From my experience, probably one-third would be high. Certainly with chronic GI disease, the presence of soft stools or multiple bowel movements a day, five bowel movements a day, may be more of an indicator of food allergy than vomiting or diarrhea.

Dr. Felsted: What do you think is the most effective way to diagnose adverse food reactions?

Dr. Garfield: I believe the only way to diagnose food allergy is with a restricted food trial. We often have patients referred to our practice that have been ELISA or RAST tested previously. I do not think I have ever seen a negative ELISA test for food antigens. I also have probably never seen one that I could rely on the results to be of diagnostic significance.

Dr. Strauss: Yes, I would say multiple studies have demonstrated that the ELISA antibody titer type test for food allergens is not diagnostic. My recommendation at this point is not to even run those tests. They are just not helpful.

Dr. Felsted: Dr. Liska, has your experience been different?

Dr. Liska: No. I still absolutely believe the best way to diagnose a food hypersensitivity is by changing to a novel protein diet or a hydrolyzed diet.

Dr. Felsted: What food options are available for dietary trials?

Dr. Liska: I spend time looking at the diet history and then use that diet history to determine what I think is the best novel protein or the best hydrolyzed diet for that patient.

Dr. Fadok: My preference is to start with a novel protein. But if the animal has already gone through a diet trial, or if there's a palatability issue, I will switch to a hydrolyzed soy diet.

Dr. Garfield: Unfortunately, it is not uncommon that by the time these patients see a specialist, they have already been exposed to multiple novel proteins. That makes it harder for us to choose a restricted or novel protein diet that is appropriate for that patient. In these instances a hydrolyzed protein diet may be useful.

Dr. Strauss: I would just categorize the diet choices as novel protein diets and hydrolyzed diets. I think there is also the home cooked option which a lot of dermatologists rely on fairly heavily. I do not use home cooked diets all that much just because compliance is an issue. I also worry about long term nutritional status of those patients.

Dr. Felsted: All of you have mentioned using novel protein diets as a way of diagnosing adverse food reactions. Are there any disadvantages?

Dr. Liska: I do try to acknowledge to my client that the restrictions we are instituting will make the next three months challenging.

Dr. Felsted: Does it usually take that long? Dr. Liska: Yes.

Dr. Garfield: I would say two months is the minimum. These patients often have secondary otitis, secondary staph folliculitis, malassezia dermatitis, all kinds of stuff going on. So it is fine to start the diet trial but you also need to treat these secondary infections, often for 4-6 weeks, to get them resolved. Then you take away the supportive therapy and see if they are able to maintain on the hypoallergenic diet alone. In some cases it can take three or four months in tough cases to get all that secondary stuff cleared up before you can take the training wheels off and see how they do with just the hypoallergenic diet.

Dr. Felsted: Novel protein diets used to be available only at veterinary practices but they are now more commercially available, for example at retail outlets where pet owners can buy them without veterinary advice. Do you think that has made your job more difficult in diagnosing and treating this condition?

Dr. Fadok: Yes, it ruins those meat sources for us.

Dr. Strauss: I think it is reflected in what proteins pets are exposed to by the time they get to us. Many times they, as Dr. Garfield pointed out, have tried some of these diets. This eliminates several proteins that can be used for a novel protein diet trial.

Dr. Felsted: Do you think clients are buying those diets because they recognize the hypoallergenic aspect or because it just sounds interesting and "Fluffy" might like this better?

Dr. Liska: I think oftentimes owners are given nonspecific recommendations such as, "Your dog needs to be on a venison-based diet." or "I would recommend a venison-based diet." They go shopping, see a venison-based diet and they think that is what their veterinarian has recommended

Dr. Felsted: They don't recognize all the other ingredients that have an impact unless somebody tells them.

Dr. Liska: There is one diet available over the counter, it is labeled as a venison based diet, but the second or third ingredient is chicken. The owner feels like they are buying a novel protein diet but it is not truly a pure diet.

Dr. Fadok: I try to tell them that it's not what you eat, it's what you don't eat.

Dr. Strauss: I emphasize to my clients what it says on the front of the bag may bear no resemblance to what the ingredient list shows. You have to read the label.

Dr. Fadok: We have clients who are not medically trained buying food without understanding what the hypoallergenic diet is meant to accomplish. They have the mistaken notion that feeding a novel protein diet has a dominant effect, and will negate the effects of treats, rawhide chew toys, etc. With an OTC brand, we don't know the quality control. We just don't know what came down the production line right before and how thoroughly the production equipment has been cleaned.

Dr. Liska: And as was pointed out by Dr. Fadok, what came down the production line prior to the production of the diet in question.

Dr. Felsted: Do you think that clients are starting to believe that they can diagnose this themselves? Are they educated enough to do that? What is the long term impact of these diets being available over the counter on diagnosis and treatment?

Dr. Liska: I would like referring veterinarians to embrace the idea that a dietary elimination trial is a diagnostic test. Just as they strive to run a low dose dexamethasone suppression test with precision, so should they perform a diet trial with high standards. The term hypoallergenic is a medical claim so appropriate diets must come from a medical office. I would like veterinarians to feel confident saying; "There is a medical basis for using prescription diets and not using over the counter brand dog foods."

Dr. Garfield: To answer your question, "Are clients educated enough to go in and make these decisions themselves?" I think the majority are certainly not able to do that.

Dr. Felsted: But they probably think they are to some extent because they only have one piece of the puzzle.

Dr. Garfield: Clients can go into the pet store and ask five different employees what food to buy for their pet with skin disease and get five different opinions. They know that veterinarians are using novel protein diets so they have some of these available there. Either the diets they purchase are not restricted enough to be of diagnostic value, or the client does not get the educational information they need to do a restricted diet trial accurately. Changing the food to a truly novel protein diet, with only one animal protein or one vegetable protein and a single carbohydrate is critical. But just as important, is that the client be educated that they cannot feed multi-ingredient dog biscuits, raw hides, table food, flavored heartworm preventatives, and cannot use "Pill Pockets" for administering medications during the food trial. The client has to understand that one bite, one lick of the other pet's food bowl, one piece of pizza crust, can exacerbate their pet's symptoms for 30 days or more. The availability of unique novel protein-containing diets over the counter has made it more difficult as a veterinary dermatologist to design an appropriate food trial for our patients. If venison and rabbit and kangaroo are put out there in the general marketplace we are going to lose those as novel proteins to be able to use as one of our main tools for diagnosing food allergy. I would like to see novel proteins not be widely available over the counter.

Dr. Felsted: Only available through a veterinary channel.

Dr. Garfield: Yes, otherwise we will have an even shorter list to choose from for diagnostic trials in the future.

Dr. Felsted: So there is a huge client educational aspect here?

Dr. Strauss: It is hard enough after you have spent half an hour of client education time to get it right. I can't imagine many people are successful doing it on their own. I emphasize to my clients what it says on the front of the bag may bear no resemblance to what the ingredient list shows. You have to read the label.

Dr. Felsted: How big of an issue is the availability of these diets over the counter for you? Is this a small issue that is making your life slightly more difficult or is this becoming a major problem?

Dr. Strauss: It is significant I would say. I don't know if it is a huge problem but it is certainly significant. You start going through the dietary history and a lot of times you just...

Pitfalls to Avoid in a Diet Trial

Dr. Felsted: They've eaten everything.

Dr. Garfield: Fifteen years ago we were using lamb as the major novel protein. Every dog food manufacturer that exists came out with a lamb-based diet down the road. As those diets came into the marketplace, every patient that came in to see us had been exposed to a lamb-based diet. It either wasn't a restricted diet, or if they were placed on a restricted lamb-based diet, they were not taken off treats, table food, or flavored medications. Therefore the diet change was not diagnostic, and the patient had then been exposed to a novel protein that we could then no longer use as a diagnostic tool. It got us away from lamb fifteen years ago which is a more readily available novel protein than kangaroo. It had just gotten us to where we couldn't use lamb at all. If that continues along the path that it appears to be with venison rabbit and kangaroo, then it is going to make it more and more difficult.

Dr. Liska: You know, perhaps we will come full circle though.

Dr. Strauss: And lamb will be okay again.

Dr. Garfield: Actually, with cats I will use lamb-based diets because at least cats aren't exposed to it as often as dogs and the palatability is good.

Dr. Felsted: When do you use hydrolyzed diets versus novel protein diets?

Dr. Strauss: I really like hydrolyzed diets. When you can't get a clear history, when you're really not sure or they have just been on so many things you can't find a novel protein diet that is going to work for this patient, I like the hydrolyzed diet.

Dr. Liska: I think not all hydrolyzed diets are created equal either. Some are not as hydrolyzed (as others) and so I am also going to choose one that has been processed to the smallest kilodalton.

Dr. Felsted: What other things do you look at when you pick your diets?

Dr. Strauss: Palatability is a big issue. Some of the earlier diets were not good.

Dr. Fadok: I have yet to see a dog turn its nose up at (Royal Canin®'s) HP. And cats, they love it.

Dr. Liska: I learned interestingly from one of the companies that the smaller they hydrolyze the protein the more bitter it tastes.

Dr. Garfield: I use hydrolyzed diets versus novel protein diets for a couple of different reasons. One would be that if I have a patient that I truly believe is food allergic and they are not improving on a novel protein diet then I will switch them and do a hydrolyzed diet. Instead of changing flavors, I change styles.

Hydrolyzed Proteins

Dr. Felsted: Do you get push back from clients on cost of food?

Dr. Strauss: Yes, especially for the bigger dogs. Some bags can cost over one hundred dollars. That is a pretty significant factor for a lot of people.

Dr. Felsted: What do you tell them to help them get over that hurdle?

Dr. Strauss: I point out that if we have to medicate the dog that is not exactly inexpensive either.

Dr. Fadok: I hear it more now than two years ago. When I'm trying to sell a food trial, I tell them it's a diagnostic tool. Once we have the answer, I tell them "You choose what you feed but you get what you pay for."

Dr. Felsted: Coming back to this multiple allergy issue, do you use diets as a component of treating atopic dermatitis where you really don't think that there is a food allergy per se? Are there diets that can help with that?

Dr. Liska: I know for example Royal Canin® has a food for the atopic patient and I have been trying that diet to see if I can further improve my patient's quality of life. If the high levels of fatty acids in the diet help my client avoid administering four capsules of fatty acid supplement then I am willing to add the diet to my medical recommendations. If I can take a patient from being a 4 out of 10 to a 2 out of 10 because I have changed the diet to something with high fatty acid level then fantastic. I have only improved the quality of that patient's life.

Dr. Felsted: What about a vegetarian diet for either dogs or cats as a hypoallergenic diet?

Dr. Fadok: There are many animals who don't do well with animal protein. Like one of our tech's dog. He flared on rabbit and potato. I switched him to (Royal Canin®) Vegetarian and he did well.

Dr. Garfield: For dogs I find it harder with comparing a vegetarian diet to the patient's dietary history to be able to say that I truly have a novel diet. I use less vegetarian diets because of that. Now, Dr. Crow in our office is using vegetarian diets quite a bit and is having some success with them.

Dr. Liska: And I am using vegetarian diets too. It was the recommendation from my peers at Gulf Coast that made me feel comfortable in utilizing those vegetarian diets.

Dr. Felsted: What do you like about vegetarian diets? What would be the advantage?

Dr. Liska: Novel protein.

Dr. Fadok: Lower fat too, for those overweight dogs.

Dr. Strauss: I have used vegetarian diets a few times and had some success

Dr. Felsted: So aside from protein and carbohydrates, what other nutritional issues do you look at when you are selecting a diet?

Dr. Strauss: It is important that these diets are carefully made and that they have very limited ingredients. When I say carefully made I like to hear that the manufacturer does everything it can to prevent cross contamination. Even small amounts of proteins from other sources can adulterate the product with other allergens. So one thing with the sort of over-the-counter foods is you don't know if they are making venison next to a beef-based diet resulting in cross contamination. You don't know that.

Dr. Felsted: What about things like fatty acids, preservatives, pre- or probiotics. How important do you think those ingredients are and how does this impact your selection of a diet?

Dr. Strauss: In an academic setting, of course, they do not want high levels of essential fatty acids. They do not want probiotics. They do not want things that affect the skin barrier because they only want to change one thing and that is the proteins that are in the diet and see if the patient gets better. I understand that argument. To me if I change the dog's diet and the dog gets better it doesn't necessarily matter to me whether that was due to the change of proteins that the dog was eating or due to the other ingredients that are in the diets. Again, from a practical standpoint if the patient gets better that is what we are all aiming for. A dietary challenge if the patient improves can help to determine if there is a food allergy or if other ingredients are helping, but often clients are reluctant to perform a food challenge.

Dr. Garfield: I agree with Dr. Strauss. I know that some of the manufacturers' marketing and production has gone in that direction and the manufacturers have shown data that with diets containing high levels of fatty acids, probiotics, etc., thirty percent or forty percent of the pruritic patients may experience an overall improvement. That is not necessarily picking out truly food allergic patients. I think from a purist standpoint, we are trying to find a direction to manage this patient, we are trying to differentiate between food allergy versus are we helping relieve symptoms with a diet that is supplemented highly in fatty acids. That does make a difference. We can get through that by doing a food challenge with the original diet and monitoring for exacerbation of symptoms within 1-7 days.

Dr.Strauss: Again, ideally they would not have those ingredients for a diet trial but all of them now have high levels of essential fatty acids

Dr. Fadok: I prefer to use diets that incorporate high levels of fatty acids because I know that the animal is actually getting them in the appropriate balance and ratio, at least to our knowledge.

Dr. Felsted: So what kinds of things do you look for in those diets? The fatty acids?

Dr. Liska: That is probably a big part of it.

Dr. Strauss: I think the essential fatty acids are the ones that have the most clinical evidence behind them. Some of the newer things ... they have shown some effect in trials, you know, barrier function type things. As Dr. Liska said, in tough cases you are always looking for that additional thing that you can do to kind of get that last 10 percent or 15 percent.

Dr. Garfield: I would agree. The high levels of fatty acids are the dietary ingredients that have been through numerous clinical trials and have the most evidence based support. B vitamins, trace minerals, and pre- and probiotics certainly have shown some evidence to improve barrier function.

Dr. Fadok: I prefer diets with elevated fatty acid levels, as well as Vitamin E and other antioxidants. Coat quality is improved and general owner satisfaction seems to be high. Quality food is one tool in our toolbox to manage the allergic patient.

Dr. Felsted: What is the issue of the skin barrier . .. that is not something I am familiar with.

Dr. Strauss: That's the newest thing - improving barrier function. They have shown now that atopic patients have impaired barrier function of their skin

Skin Barrier Function

Dr. Felsted: And that means exactly what?

Dr. Strauss: Well basically that the skin barrier is more permeable to water. So the thought is that this may allow transepidermal absorption of an environmental allergen.

Dr. Garfield: Besides the allergen absorption, if barrier function is abnormal the skin surface is more likely to colonize with staphylococcal bacteria and with malassezia yeast adding to the patients symptoms. So improving barrier function may decrease allergen absorption and help prevent secondary infections. That can be done from the inside out with dietary supplementation or from the outside in with emollients and ceramides applied topically to the skin through shampoos, sprays, topical spot on products, etc.

Dr. Felsted: But, it would be easier to do with food, wouldn't it, then have to do from the outside in?

Dr. Garfield: Absolutely.

Dr. Strauss: Now there are a lot of supplements and ingredients that they put in foods that have been shown to have some affect on barrier function.

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