S Y M P O S I U M
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S Y M P O S I U M
SYMPOSIUM PEER-REVIEWED Allergy testing and treatment for canine atopic dermatitis Now that you’ve diagnosed atopic dermatitis, how do you alleviate the patient’s suffering? Allergen-specific immunotherapy, which requires allergy testing, holds the best chances for relief, but symptomatic treatment can help as well. ANDREW HILLIER, BVSc, MACVSc, DACVD Department of Veterinary Clinical Sciences College of Veterinary Medicine The Ohio State University Columbus, OH 43210-1089 AS DISCUSSED in the first article in this symposium, the diagnosis of atopic dermatitis is based on a suggestive history, typical clinical signs, and ruling out differential diagnoses. Positive allergy test results are not a prerequisite for diagnosis. Allergy tests are most useful in selecting allergens for allergen-specific immunotherapy and in determining allergen-avoidance measures. The options for treating and controlling atopic dermatitis include allergen avoidance, allergen-specific immunotherapy, symptomatic antiinflammatory therapy, and antimicrobial therapy. The treatment selected and the response to it differ from animal to animal depending on the nature and intensity of clinical signs and flare factors (e.g. pyoderma, yeast dermatitis, otitis); the patient’s tolerance of repeated topical, oral, or injectable treatment; and the owner’s willingness to accept the time, effort, and expense of treatment. Anti-inflammatory therapy alone may be adequate in dogs with a short and confined allergy season, in dogs responsive to nonsteroidal symptomatic therapy, or in dogs in which intermittent low-dose alternate-day prednisone controls clinical signs without side effects. But 210 MARCH 2002 Veterinary Medicine most dogs with atopic dermatitis have nonseasonal disease, are inadequately controlled with symptomatic therapy alone, or have unacceptable side effects from symptomatic therapy. In these circumstances, allergen-specific immunotherapy is the primary therapeutic option. As response to immunotherapy is allergen-specific,1,2 allergy testing is necessary to determine which allergens are causing disease in a patient. This is the true indication for allergy testing. Allergy testing Two types of allergy tests are available: intradermal tests (skin tests), and allergen-specific IgE serology (serum tests). Although widely used, the term allergy test is a misnomer. Neither intradermal tests nor allergen-specific IgE serology definitively rule in or rule out allergy (i.e. clinical disease). Rather, they are useful in demonstrating IgE-mediated hypersensitivity to allergens that may be causing skin disease, such as atopic dermatitis (true allergy), or that are not causing disease (subclinical hypersensitivity), as seen in normal dogs that can have positive allergy tests.3,4 This is the principal reason why allergy tests cannot be used as a screening test at the initial consultation. There has been much debate concerning the usefulness of intradermal testing and allergen-specific IgE serology and the advantages of one over the other. Historically, intradermal testing has been considered the gold standard, and the accuracy of allergen-specific IgE serology is often evaluated by comparative analysis with the results of intradermal testing.5 This is perhaps unfair, because intradermal testing detects IgE in the skin, and allergen-specific IgE serology detects IgE in the serum. The two are not necessarily equivalent. Also, in veterinary medicine, allergen extracts, testing methodologies, and interpretation of results have not been standardized for either intradermal testing or allergen-specific IgE serology. Neither test has been demonstrated to be superior to the other. Both intradermal testing and allergen-specific IgE serology offer the potential for useful information when performed and interpreted according to broadly defined accepted criteria. Generally, there is a fairly good correlation between the results of the separate tests in individual animals. But some dogs with positive reactions on intradermal testing have negative results on allergen-specific IgE serology, and vice versa. I routinely perform both intradermal testing and allergen-specific IgE serology when allergen-specific immunotherapy is anticipated. Since most general practitioners do not perform intradermal testing, further discussion is focused on allergen-specific IgE serology. The general principles of allergy test result interpretation are similar for both intradermal testing and allergenspecific IgE serology. SYMPOSIUM Treating canine atopic dermatitis (cont’d) Choosing a serum-based allergy test Numerous laboratories and companies offer allergen-specific I g E serology. When choosing a laboratory, consider the scientific basis of the assay, the published results of studies using the assay, the laboratory’s involvement in allergy research, the quality and efficiency of the service, the availability of qualified technical staff for consultation, and the cost. There are marked differences among the assays performed by each of the laboratories, including the allergen source, the reacting phase (liquid or solid), the IgE-specific detection reagent (e.g. monoclonal antibody, polyclonal antibody, α chain of IgE receptor), and the methods of calculating, reporting, and interpreting results. The effect and importance of differing assays have not been criti- cally evaluated in controlled independent studies, and claims of superiority of one assay over another need to be interpreted with extreme caution.5 In general, most allergen-specific IgE serology assays have good sensitivity (ability to identify true allergen hypersensitivity) but seem to have variable and lower specificity (ability to correctly identify the absence of allergen hypersensitivity).5 Low specificity is associated with false positive results, possibly resulting in an incorrect diagnosis and incorrect formulation of allergen-specific immunotherapy. An in-clinic screening test has recently been released that detects the presence of allergen-specific I g E (Allercept E-Screen—Heska). This test is designed to be a guide in determining whether further full allergen-specific IgE serology is indicated. This test should only be used once a clinical diagnosis of atopic dermatitis has been made; do not use it to screen for atopic dermatitis at the initial visit. It may be useful as a relatively inexpensive test to convince owners who are reluctant to spend money on full allergen-specific IgE serology that such testing is warranted. Further, this screening test may be useful in determining whether it is an appropriate time for a full test. Independent analysis of this test has not been published to date, and its sensitivity and specificity have yet to be studied. despite the fact that studies suggest allergen-specific IgE serology is not helpful in diagnosing cutaneous adverse food reactions.6,7 These tests also do not appear to be of value in determining which foods to avoid in a food trial. Thus, they should not be used in place of appropriate hypoallergenic elimination diet food trials. Interpreting positive test results You must determine which positive results of allergy testing (if any) are of clinical relevance in each case and, thus, which allergens should be included in allergen-specific immunotherapy. Examine the medical record to determine whether the pattern of the disease is seasonal or nonseasonal, and ask the owner about the exact nature of the dog’s habitat and likely exposure to those allergens within the dog’s environment. In general, allergens may be categorized as8: • Nonseasonal: house dust mites (Dermatophagoides species), storage mites (e.g. Tyrophagus, Lepidoglyphus, and Acarus species), cockroaches, moths, dander or epidermals, and indoor molds (Penicillium, Aspergillus, Rhizopus, and Mucor species) • Spring: tree pollens • Summer: grass pollens and outdoor molds (Alternaria and Cladosporium species) • Fall: weed pollens and outdoor molds. Food allergen testing The history and clinical signs of cutaneous adverse food reactions are often identical to those of atopic dermatitis, and a hypoallergenic food trial is necessary to distinguish between the two diseases. In addition, some dogs with atopic dermatitis have concurrent cutaneous adverse food reactions. Most laboratories offer food allergen panels for serum testing 212 MARCH 2002 Veterinary Medicine Some nonseasonal allergens may be more abundant at certain times of the year, such as house dust mites in the summer and fall and indoor molds during more humid times of the year. Information on pollen seasons in different regions can be obtained by visiting the National Allergy Bureau’s Web site at www.aaaai .org/nab/ or visiting www.pollen.com. SYMPOSIUM Treating canine atopic dermatitis (cont’d) TABLE 1 Allergen Avoidance and Control Measures House dust mites Cover mattresses, pillows, dog beds, chairs, and sofas with impermeable covers (vinyl). Remove clutter, such as stuffed animals, from the pet’s sleeping areas to prevent dust accumulation and to facilitate thorough cleaning. Do not allow the pet into areas in which dust typically accumulates, such as closets, the laundry room, and under the beds. Vacuum the house with a HEPA filter as frequently as possible—at least weekly. Keep the pet outdoors during vacuuming and for one hour afterward. Remove as many carpets and rugs as possible, especially from poorly ventilated rooms such as the basement, garage, and laundry room. Wash linen, bedding, and blankets every week in hot water (> 130 F [54.4 C]). Keep the humidity in the home at 30% to 45% relative humidity by using a dehumidifier, air conditioning, or a humidifier when needed. Molds Keep the dog away from freshly mowed grass, mulch, leaf piles, hay, and barns. Keep the dog’s kennel dry and clean. out the year, but inconclusive or negative results may be seen outside of the optimal times. • Important allergens were not included in the allergy test. Storage mites may be important allergens in dogs in the United States,14 as they are in Europe.15-18 But these mites are not routinely included in allergen-specific IgE serology and intradermal tests in the United States. • A small percentage of dogs with atopic dermatitis are thought to have persistently negative allergy test results. This is unproved in dogs but a known fact in people with atopic diseases. Keep the humidity in the home at 30% to 45% relative humidity. Keep the pet out of basements, closets, the laundry room, and bathrooms. Keep the pet’s bedding clean and dry. Allergen avoidance Store food in a dry environment. Clean moist areas where molds thrive with a fungicide or dilute sodium hypochlorite solution (1 part bleach to 9 parts water). Interpreting negative test results If allergy test results are negative or if positive results do not correlate with a patient’s disease, consider these possibilities: • The dog does not have atopic dermatitis. Make sure you’ve appropriately ruled out flea allergy dermatitis, cutaneous adverse food reactions, scabies, insect bite hypersensitivity, and contact dermatitis. • Alternative allergy testing may be indicated (i.e. intradermal testing if only allergen-specific IgE serology was performed, or vice versa). • Certain drugs can interfere with allergy testing. Antihistamines are known to affect intradermal tests9 but not allergen-specific IgE serology. Corticosteroids are also known to affect intradermal tests.10,11 Preliminary evidence 214 MARCH 2002 Veterinary Medicine Treatment suggests that glucocorticoids do not affect allergen-specific IgE serology results.12,13 Since this is purported as an advantage of allergen-specific I g E serology over intradermal testing, more extensive studies are necessary to confirm these initial findings. Also, cyclosporine is likely to affect both intradermal testing and allergen-specific IgE serology, although this has not yet been studied in dogs. • It may be the wrong time of year for allergy testing in this patient. The peak of the allergy season (highest I g E levels) is best for allergen-specific I g E serology. Toward the end or shortly after the peak allergy season is best for intradermal testing. Both allergen-specific IgE serology and intradermal testing are usually performed through- Table 1 provides guidelines you can give owners that may help reduce the allergen load and exposure in patients hypersensitive to house dust mites and mold.19 These guidelines will help owners decide how much time, effort, and expense they want to invest in these avoidance measures. The guidelines are based on recommendations in people with allergies. They have not been evaluated in controlled studies in dogs. However, in several of my patients, skin disease improved after their owners implemented these measures. Allergen-specific immunotherapy Allergen-specific immunotherapy (also known as hyposensitization or desensitization) is the practice of administering gradually increasing quantities of an allergen extract to an allergic subject to ameliorate the signs associated with subsequent exposure to the causative allergen.20 Allergens are given by subcutaneous injection in increasing doses up to a maintenance dose or a patient- SYMPOSIUM Treating canine atopic dermatitis (cont’d) determined maximum dose. The mechanism of action of this treatment has not been determined in dogs. Some of the advantages of allergen-specific immunotherapy compared with conventional symptomatic therapy (see below) include a lower frequency of administration, a low risk of long-term side effects, and the potential to permanently alter the course of the disease. In addition, allergen-specific immunotherapy is often more cost-effective long term. But some owners may be reluctant to give injections, and some dogs will not accept repeated injections. In these cases, injections may be given at the clinic by the veterinarian. There is also a very low risk of anaphylaxis. As no blinded randomized trials of allergen-specific immunotherapy with aqueous allergens have been reported, the true efficacy of allergenspecific immunotherapy in canine atopic dermatitis is unknown. Numerous open uncontrolled studies imply that between 50% and 100% of dogs treated with allergen-specific immunotherapy will have at least a 50% improvement in clinical signs.21-34 Further, open studies have reported that factors such as the age at onset, age at the time of allergen-specific immunotherapy initiation, duration of disease, severity of clinical signs, breed, strength of intradermal testing or allergen-specific IgE serology reactions, number of intradermal testing or allergen-specific IgE serology reactions, and type of allergen to which a patient is hypersensitive may be predictive of the outcome of allergenspecific immunotherapy.23-25,29-31,34,35 These observations remain to be validated in controlled studies. Allergen-specific immunotherapy is indicated in any dog with nonseasonal atopic dermatitis or any dog with seasonal atopic dermatitis in 216 MARCH 2002 Veterinary Medicine which symptomatic therapy is ineffective, is associated with unacceptable side effects, or cannot be maintained for extended periods. Since allergenspecific immunotherapy is administered most often at home, owners need to be prepared to accept the technical aspects of the treatment, observe the dog for side effects, maintain the protocol as prescribed, and present the dog for regular rechecks. Concurrent therapy Glucocorticoids and cyclosporine, sometimes given in dogs with atopic dermatitis as symptomatic therapy, have multiple effects on the immune reaction. The consequences of these effects on the response to allergenspecific immunotherapy have not been specifically studied, but it may be best to avoid their use, especially during the initial phases of allergenspecific immunotherapy. Protocols As none of the variables (e.g. dose of allergen, dosing interval) associated with allergen-specific immunotherapy have been studied in controlled experiments, it is impossible to make definitive recommendations. There are no data proving that one protocol is better than another. Unlike in most conventional drug therapies, the pharmacokinetic characteristics of allergenspecific immunotherapy have not been rigorously studied. By convention or habit, most protocols follow these guidelines: • There can be 10 to 12 allergens per vaccine. • The initial loading phase starts with a low dose of allergen (200 to 2,000 PNU/ml) given subcutaneously every two to seven days with incremental increases in allergen dose. • A maintenance dose of 10,000 to 20,000 PNU/ml is given every one to three weeks. Some dogs start to improve within a few weeks, but most take many months. Allergen-specific immunotherapy should be continued for at least one year before the full effects may be appreciated or a lack of response is assessed. If the immunotherapy is efficacious, continue it for the life of the dog. If it fails to improve clinical signs after one year, reevaluate the patient (see below). Safety and adverse reactions Localized swelling, erythema, pain, or pruritus may be seen at the injection site. Pretreatment with antihistamines may help control these reactions.20 The most common systemic reaction is a worsening of clinical signs, especially pruritus.20 Other reported systemic reactions include weakness, depression, anxiety, vomiting, diarrhea, urticaria, and angioedema. Rarely, but importantly, anaphylaxis may occur, with collapse and possibly fatal consequences. Be sure to inform owners of the clinical signs of such reactions, and advise them to observe their dogs for one hour after each injection. If any clinical signs appear, urgent care is necessary. Recheck evaluations Recheck examinations are one of the most overlooked aspects of allergen-specific immunotherapy. Reevaluating dogs receiving allergenspecific immunotherapy after one, three, six, and 12 months (ideally, but at least after three and 12 months) will be helpful in realizing optimal results. Patient monitoring is essential, because perpetuating factors (e.g. staphylococcal pyoderma, yeast dermatitis, otitis) are likely to recur until there is marked response to allergen-specific immunotherapy, which may take months. Also, owners may neglect to control concurrent SYMPOSIUM Treating canine atopic dermatitis (cont’d) diseases (e.g. flea allergy dermatitis, cutaneous adverse food reactions, insect hypersensitivity) as they concentrate on allergen-specific immunotherapy. In addition, compliance by owners in following the injection protocol is reportedly low.32,36 Regular rechecks will improve compliance. Troubleshooting At each recheck, ask the owner to describe any changes observed after each injection as well as any overall changes in pruritus. If the pruritus initially decreases after each injection but then slowly increases again before the next injection, the effects of the allergen-specific immunotherapy are lasting for only a short time after each injection. In this case, the interval between injections should be decreased, and subsequent injections should be administered when the increase in pruritus is expected. If the pruritus initially increases after each injection, followed by improvement before the next injection, the allergen dose is too high and is inducing pruritus. Decrease the dose of allergen by 25%. If the spike in pruritus after the injection is still present, decrease the dose by 25% again. At the six- and 12-month recheck examinations, review the maintenance protocol. If the pruritus has decreased overall but is still marked, the allergen dose may be too high or too low. Start by decreasing the dose of allergen by 25%. If there is a further reduction in pruritus, continue to decrease the dose by 25% until pruritus is minimal or eliminated. If the initial decrease of 25% increases the pruritus, then increase the maintenance dose by 25%. If the pruritus decreases, continue to increase the dose by 10% to 25% each time until the pruritus is minimal or eliminated. Be especially observant for side effects when increasing the dose. 218 MARCH 2002 Veterinary Medicine If a dog is worse at either the sixor 12-month recheck examination, do not increase the allergen dose. Check for any perpetuating factors (e.g. pyoderma, yeast dermatitis) or concurrent diseases (e.g. flea allergy dermatitis, cutaneous adverse food reactions, scabies, insect hypersensitivity). Once these factors have been controlled, decrease the allergen dose by 50%. If there is a decrease in pruritus, decrease the dose by 50% at each subsequent injection until the pruritus is minimal or eliminated. Symptomatic therapy Based on limited controlled studies and a large body of anecdotal evidence, symptomatic therapy may be divided into three broad categories. The first category includes drugs with weak evidence of efficacy in treating atopic dermatitis, including antihistamines, antidepressants, essential fatty acids, and topical anti-inflammatory therapy. These drugs are widely recommended, may be highly efficacious in a few patients, and are mostly relatively safe and inexpensive. The next category includes drugs with fair evidence of efficacy in treating atopic dermatitis, including phosphodiesterase inhibitors and misoprostol. The evidence for the efficacy of these drugs is currently limited to a few small studies. The final category includes drugs with good evidence of efficacy in treating atopic dermatitis, including glucocorticoids and cyclosporine. The evidence for the efficacy of these drugs is limited to a few small studies. These treatments often carry a higher risk for side effects, and they may be expensive. For dogs with limited seasonal disease or mild clinical signs or for dogs early in the course of the disease, try first-category drugs initially and then second-category drugs, if necessary. For dogs starting allergen-specific im- munotherapy (before it has had any effect), try first- and second-category drugs initially, and only use glucocorticoids sparingly if absolutely necessary. For dogs with moderate to severe disease or nonseasonal disease in which allergen-specific immunotherapy is not being pursued or for dogs that have not responded to allergenspecific immunotherapy, try first- and second-category drugs first; but the third category of drugs are often necessary. For crisis situations in which pruritus is severe, try glucocorticoids in short, aggressive, “crisis-busting” doses (possibly in combination with drugs in the first and second categories); apply Elizabethan collars; or use T-shirts or bodysuits as barriers. These recommendations vary in each case according to response to treatment; owners’ expectations, compliance, and ability to treat their dogs; cost considerations; and side effects or adverse reactions. First-category drugs Few well-controlled studies demonstrate the efficacy of antihistamines in treating atopic dermatitis, despite their widespread use.37 Table 2 lists some of the more commonly used antihistamines. The response varies from dog to dog and antihistamine to antihistamine. Some dogs do not respond to any antihistamine, while a minority have an excellent response. Each antihistamine should be tried for at least seven to 14 days. Side effects of antihistamine treatment include sedation, trembling, hyperesthesia, salivation, excitation, and panting. Synergistic effects with glucocorticoids have been suggested, potentially allowing for a decrease in glucocorticoid requirement in some dogs. 38 For this reason, in some glucocorticoid-dependent patients I use trimeprazine tartrate and prednisolone (Temaril-P—Pfizer; trimep- SYMPOSIUM Treating canine atopic dermatitis (cont’d) TABLE 2 Antihistamines Commonly Used to Treat Canine Atopic Dermatitis Antihistamine Trade Name Dosage Hydroxyzine hydrochloride Atarax (Pfizer), generics 2.2 mg/kg orally t.i.d. Diphenhydramine hydrochloride Benadryl (Warner-Lambert), generics 2.2 mg/kg orally t.i.d. Clemastine fumarate Tavist Allergy (Novartis Consumer), generics 0.05–0.1 mg/kg orally b.i.d. Chlorpheniramine maleate Chlortrimeton, generics 0.2–0.5 mg/kg orally b.i.d. to t.i.d. Cyproheptadine hydrochloride Periactin (Merck), generics 0.3–2 mg/kg orally b.i.d. Promethazine hydrochloride Phenergan (Wyeth-Ayerst), generics 0.2–1 mg/kg orally b.i.d. to t.i.d. razine 5 mg, prednisolone 2 mg) at a dosage of 1 tablet/10 kg (maximum of three tablets) every 12 hours given orally for seven days and then tapered to the lowest possible dose every other day. Synergistic effects with essential fatty acids have also been suggested.39 Two antidepressants have been used in dogs with atopic dermatitis. Doxepin hydrochloride (0.5 to 2 mg/kg orally b.i.d.), a tricyclic antidepressant, may be helpful in some dogs with atopic dermatitis because of its potent antihistaminic effects, anticholinergic effects, and serotonin reuptake inhibition. Fluoxetine hydrochloride (1 mg/kg orally once a day), a selective serotonin reuptake inhibitor, has also been studied, with contradictory results.40,41 Disadvantages of fluoxetine include side effects (e.g. excitation, polydipsia, polyuria, lethargy) and a three- to four-week period until an effect is seen. Two types of essential fatty acids have been used to treat dogs with atopic dermatitis. Omega-6 fatty acids (most common in vegetable oils) are potentially useful in correcting epidermal lipid barrier defects that are suspected to be present in dogs with atopic dermatitis. Omega-3 fatty acids (marine oils, flaxseed oils) are potentially useful in atopic dermatitis be220 MARCH 2002 Veterinary Medicine cause of their modulatory effects on eicosanoid production and other immunomodulatory properties. Despite more than 20 studies, the true efficacy of essential fatty acids remains uncertain, as most studies are inadequately designed and controlled.42 An omega3 fatty acid (eicosapentaenoic acid 40 mg/kg orally once a day)43 may be best for anti-inflammatory effects. Omega-6 fatty acids (60 to 138 mg/kg orally once a day)42 may be best to restore the epidermal lipid barrier if dry skin is a prominent clinical sign. Numerous topical anti-inflammatory agents are available for use in dogs with pruritic and inflammatory skin disease, including corticosteroids (e.g. hydrocortisone, fluocinolone acetonide, triamcinolone acetonide, dexamethasone, betamethasone), antihistamines (e.g. diphenhydramine hydrochloride), local anesthetics (e.g. pramoxine hydrochloride), colloidal oatmeal, capsaicin, menthol, aloe vera, moisturizing agents, and antimicrobial agents (e.g. chlorhexidine, benzoyl peroxide, ethyl lactate, miconazole, ketoconazole). These are available in various formulations, including shampoos, rinses, sprays, lotions, and leaveon conditioners. Their use is usually limited to dogs with localized disease, where owners can apply the product on a regular (often daily) basis. These products are usually used in conjunction with systemic treatment. I favor leave-on conditioners with glucocorticoids or local anesthetics for localized treatment of pruritic areas; antimicrobial shampoos in dogs with a history of staphylococcal pyoderma or Malassezia dermatitis; and, for routine bathing, hypoallergenic moisturizing shampoos to remove irritants and allergens. Long-term or excessive use of topical corticosteroids may cause local or systemic side effects of hypercortisolism, so carefully monitor their use. Second-category drugs Pentoxifylline (10 mg/kg orally b.i.d.), a phosphodiesterase inhibitor that inhibits proinflammatory cytokines (e.g. tumor necrosis factor-α, interleukin-1, interleukin-6), was found to significantly decrease pruritus and erythema in 10 dogs with atopic dermatitis.44 No side effects were reported. Arofylline, another phosphodiesterase inhibitor, was found to be as effective as prednisone in controlling pruritus in 40 dogs with atopic dermatitis,45 but many dogs had gastrointestinal side effects and were withdrawn from the study. For this reason, arofylline is currently not recommended. Misoprostol is a synthetic prostaglandin E1 analogue with potent antiinflammatory properties. An initial study with misoprostol (3 to 6 µg/kg orally t.i.d.) on a small number of dogs with atopic dermatitis reported a decrease in pruritus of at least 50% in 56% of the dogs and a similar decrease in skin lesions in 61% of the dogs.46 A median decrease in pruritus and lesions of 30% was reported in another study.47 Third-category drugs Despite widespread use (and misuse) of glucocorticoids, only a few studies have evaluated their clinical efficacy in treating canine atopic dermatitis. Prednisone given orally at 0.4 mg/kg once a day for seven days gave a good to excellent response in 57% of dogs in one study,38 while prednisolone given orally at a dose of 0.5 mg/kg once a day for 30 days produced a 69% reduction of lesion scores and an 81% decrease in pruritus in another study of dogs with atopic dermatitis.48 Long-acting injectable glucocorticoids are widely used, but no studies have been conducted to critically assess their efficacy. Because of their high potency, duration of effects, and propensity to induce unacceptable side effects, these long-acting injectable glucocorticoids are not recommended for treating atopic dermatitis. Oral shortacting glucocorticoids, such as prednisone, are indicated for use as crisis busters in cases of severe exacerbation and flare of pruritus (0.5 to 1 mg/kg once a day for three days) or for longer-term control of chronic atopic dermatitis that is not adequately controlled by alternative therapies (reducing doses to < 0.5 mg/kg every other day). Cyclosporine is a calcineurin inhibitor with potent antiallergic and immunosuppressive properties.49 In dogs with atopic dermatitis, improvements in clinical lesions and pruritus similar to those achieved with oral prednisolone have been achieved at a dose of 5 mg/kg given orally once a day.48 Treatment for a minimum of 30 days may be necessary before full clinical effects are appreciated. Dogs do not appear to be prone to the hepatotoxic and nephrotoxic side effects seen in people. Side effects that may occur include vomiting, diarrhea, increased susceptibility to bacterial infections, increased incidence of neoplasia, gingival hyperplasia, and bone marrow suppression. Cyclosporine is metabolized by the PVeterinary Medicine MARCH 2002 221 SYMPOSIUM Treating canine atopic dermatitis (cont’d) 450 enzyme system, so concurrent use of drugs with effects on this enzyme system need to be considered with caution. Currently, the cost of cyclosporine is high. Conclusion Atopic dermatitis is a disease that is controlled and rarely cured, so the aim is to find a treatment that is efficacious and sustainable and that has minimal side effects. Various trials and combinations of treatments are usually necessary before a combination of treatments is found that is acceptable. The clinical signs can be extremely difficult to control in some dogs, and referral to a dermatologist should be presented to owners as an option. Editors’ note: Dr. Hillier has participated and is now participating in collaborative research studies with Heska Corporation. REFERENCES 1. Norman, P.S.; Lichtenstein, L.M.: The clinical and immunologic specificity of immunotherapy. J. Allergy Clin. Immunol. 61 (6):370-377; 1978. 2. Anderson, R.K.; Sousa, C.A.: Workshop report 7: In vivo vs. in vitro testing for canine atopy. Advances in Veterinary Dermatology, Vol. II (P.J. Ihrke et al., eds.). Pergamon Press, Tarrytown, N.Y., 1993; pp 425-427. 3. Codner, E.C.; Lessard, P.: Comparison of intradermal allergy test and enzyme-linked immunosorbent assay in dogs with allergic skin disease. JAVMA 202 (5):739-743; 1993. 4. Lian, T.M.; Halliwell, R.E.W.: Allergenspecific IgE and IgGd antibodies in atopic and normal dogs. Vet. Immunol. Immunopathol. 66:203-223; 1998. 5. DeBoer, D.J.; Hillier, A.: The ACVD task force on canine atopic dermatitis (XVI): Laboratory evaluation of dogs with atopic dermatitis with serum-based “allergy” tests. Vet. 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Macina, M.; Helton-Rhodes, K.: An investigation on the influence of corticosteroids on antigen-specific IgE and total serum IgE in dogs using ELISA allergy testing (abst.). Proc. AAVD/ACVD, AAVD/ACVD, Santa Fe, N.M., 1995; pp 32-33. 13. Miller, W.H. et al.: The influence of oral corticosteroids or declining allergen exposure on serologic allergy test results. Vet. Dermatol. 3:237-244; 1992. 14. Hillier, A.: IgE-mediated hypersensitivity to Tyrophagus putrescentiae and Lepidoglyphus destructor storage mites in dogs in the USA (abst.). Vet. Dermatol. 12:239; 2001. 15. Vollset, I. et al.: Immediate type hypersensitivity in dogs induced by storage mites. Res. Vet. Sci. 40 (1):123-127; 1986. 16. Sture, G.H. et al.: Canine atopic disease: The prevalence of positive intradermal skin tests at two sites in the north and south of Great Britain. Vet. Immunol. Immunopathol. 44:293-308; 1995. 17. Saridomichelakis, M.N. et al.: Canine atopic dermatitis in Greece: Clinical observations and the prevalence of positive intradermal test reactions in 91 spontaneous cases. Vet. Immunol. Immunopathol. 69 (1):61-73; 1999. 18. Noli, C.; Hillier, A.: House dust mites and allergy. Advances in Veterinary Dermatology, Vol. IV (K. Thoday et al., eds.). Butterworth Heinemann, Oxford, U.K. (in press). 19. Platts-Mills, T.A.E. et al.: The role of intervention in established allergy: Avoidance of indoor allergens in the treatment of chronic allergic disease. J. Allergy Clin. Immunol. 106 (5):787-804; 2000. 20. Griffin, C.E.; Hillier, A.: The ACVD task force on canine atopic dermatitis (XXIV): Allergen-specific immunotherapy. Vet. Immunol. Immunopathol. 81:363-383; 2001. 21. Halliwell, R.E.W.: Atopic disease in the dog. Vet. Rec. 89 (8):209-214; 1971. 22. Halliwell, R.E.W.: Hyposensitization in the treatment of atopic disease. Current Veterinary Therapy VI Small Animal Practice (R.W. Kirk, ed.). W.B. Saunders, Philadelphia, Pa., 1977; pp 537-541. 23. Nesbitt, G.H.: Canine allergic inhalant dermatitis: A review of 230 cases. JAAHA 172:5560; 1978. 24. Reedy, L.M.: Canine atopy. Compend. Cont. Ed. 1:550-556; 1979. 25. Scott, D.W.: Observations on canine atopy. JAAHA 17:91-100; 1981. 26. Scott, K.V. et al.: A retrospective study of hyposensitization in atopic dogs in a flea-scarce environment. Advances in Veterinary Dermatology, Vol. II (P.J. Ihrke et al., eds.). Pergamon Press, Tarrytown, N.Y., 1993; pp 79-87. 27. Sousa, C.A.; Norton, A.L.: Advances in methodology for diagnosis of allergic skin disease. Vet. Clin. North Am. (Small Anim. Pract.) 20 (6):1419-1427; 1990. 28. Miller, W.H. et al.: Evaluation of the performance of a serologic allergy system in atopic dogs. JAAHA 29:545-550; 1993. 29. Mueller, R.S.; Bettenay, S.V.: Long-term immunotherapy of 146 dogs with atopic dermatitis—A retrospective study. Aust. Vet. Pract. 26:128-132; 1996. 30. Schwartzman, R.M.; Mathis, L.: Immunotherapy for canine atopic dermatitis: Efficacy in 125 atopic dogs with vaccine formulation based on ELISA allergy testing. J. Vet. Allergy Clin. Immunol. 5:144-152; 1997. 31. Nuttall, T.J. et al.: Retrospective survey of allergen immunotherapy in canine atopy. Vet. Rec. 143 (5):139-142; 1998. 32. Rosser, E.J.: Aqueous hyposensitization in the treatment of canine atopic dermatitis: A retrospective study of 100 cases. Advances in Veterinary Dermatology, Vol. III (K.W. Kwochka et al., eds.). Butterworth Heinemann, Boston, Mass., 1998; pp 169-176. 33. Park, S. et al.: Comparison of response to immunotherapy by intradermal skin test and antigen-specific IgE in canine atopy. J. Vet. Med. Sci. 62 (9):983-988; 2000. 34. Willemse, A. et al.: Effect of hyposensitization on atopic dermatitis in dogs. JAVMA 184 (10):1277-1280; 1984. 35. Griffin, C.E.: Hyposensitization. Calif. Vet. 52:18-21; 1998. 36. Power, H.T.: Why do owners discontinue immunotherapy? (abst.) Vet. Dermatol. 11 (suppl. 1):14; 2000. 37. DeBoer, D.J.; Griffin, C.E.: The ACVD task force on canine atopic dermatitis (XXI): Antihistamine pharmacotherapy. Vet. Immunol. Immunopathol. 81:323-329; 2001. 38. Paradis, M. et al.: Further investigations on the use of nonsteroidal and steroidal antiinflammatory agents in the management of canine pruritus. JAAHA 27:44-48; 1991. 39. Paradis, M. et al.: The efficacy of clemastine (Tavist), a fatty acid-containing product (Derm Caps), and the combination of both products in the management of canine pruritus. Vet. Dermatol. 2:17-20; 1991. 40. Shoulberg, N.: The efficacy of Prozac (fluoxetine) in the treatment of acral lick granulomas and allergic inhalant dermatitis in canines (abst.). Proc. AAVD/ACVD, AAVD/ACVD, San Francisco, Calif., 1990; pp 31-32. 41. Melman, S.A.: Prozac (fluoxetine), Zoloft (sertraline) and Anafranil (clomipramine) use in animals for selected dermatological and behavioral conditions (abst). Proc. AAVD/ACVD, AAVD/ACVD, Santa Fe, N.M., 1995; p 82. 42. Olivry, T. et al.: The ACVD task force on canine atopic dermatitis (XXIII): Are essential SYMPOSIUM Treating canine atopic dermatitis (cont’d) fatty acids effective? Vet. Immunol. Immunopathol. 81:347-362; 2001. 43. Logas, D.; Kunkle, G.A.: Double-blinded crossover study with marine oil supplementation containing high-dose eicosapentaenoic acid for the treatment of canine pruritic skin disease. Vet. Dermatol. 5:99-104; 1994. 44. Marsella, R.; Nicklin, C.F.: Double-blinded placebo-controlled crossover study on the effects of pentoxifylline in canine atopy. Vet. Dermatol. 11:255-260; 2000. 45. Ferrer, L. et al.: Clinical anti-inflammatory efficacy of arofylline, a new selective phosphodiesterase-4 inhibitor, in dogs with atopic dermatitis. Vet. Rec. 145 (7):191-194; 1999. 46. Olivry, T. et al.: Treatment of atopic dermatitis with misoprostol, a prostaglandin E-1 analogue—An open study. J. Dermatol. Treat. 8:243-247; 1997. 47. Olivry, T. et al.: A placebo-controlled, blinded trial of misoprostol therapy for canine atopic dermatitis: Effects on dermal cellularity and cutaneous tumor necrosis factor-alpha gene transcription (abst.). Vet. Dermatol. 11:21; 2000. 48. Olivry, T. et al.: Cyclosporin-A decreases skin lesions and pruritus in dogs with atopic dermatitis: A prednisolone-controlled blinded trial (abst.). Vet. Dermatol. 11:19; 2000. 49. Gregory, C.L.: Immunosuppressive agents. Current Veterinary Therapy XIII Small Animal Practice ( J.D. Bonagura, ed.). W.B. Saunders, Philadelphia, Pa., 2000; pp 509-513. has been proven superior to the other. 2. Which statement is true of positive allergy test results? a. They are only seen in dogs with clinical allergy. b. They indicate clinical or subclinical hypersensitivity. c. They are never seen in dogs with nonallergic skin disease. d. They are never seen in healthy, normal dogs. e. None of the above 3. Which of these statements is true? a. Tree pollen hypersensitivity is associated with fall allergies. b. Grass pollen hypersensitivity is associated with winter allergies. c. Weed pollen hypersensitivity is associated with spring allergies. d. Outdoor mold hypersensitivity is associated with spring allergies. e. Cockroach hypersensitivity is associated with nonseasonal allergies. Article #2 4. Which of the following may be the cause of negative allergy test results in a dog with atopic dermatitis? a. Serum testing was done during the peak of the allergy season. b.Concurrent scabies suppressed intradermal test reactions. c. Important allergens were absent from the allergen test panel. d. Antihistamine interference affected the serum allergy test results. e. Skin testing was performed shortly after the peak of the allergy season. 1. Which statement regarding allergy tests is true? a. Intradermal tests are superior to serologic tests. b. Serologic tests are superior to intradermal tests. c. Correlation between serologic and intradermal test results is close to 100%. d. Correlation between serologic and intradermal test results is very poor. e. Neither intradermal nor serologic testing 5. Which statement is true of allergenspecific immunotherapy? a. It is ineffective in dogs with disease of more than five years’ duration. b. Specific protocols have been studied and defined. c. Response to treatment is seen within three months. d. Efficacy has not been established in randomized controlled studies. CE Q UESTIONS 2 CE hours You can earn two hours of Continuing Education credit from Kansas State University by answering the following questions on treating canine atopic dermatitis. Circle only the best answer for each question, and transfer your answers to the form on page 241. 224 MARCH 2002 Veterinary Medicine e. If effective, it can be discontinued after one year. 6. The most common side effect(s) from allergen-specific immunotherapy is (are): a. Anaphylaxis and collapse b. Severe local swelling, skin necrosis, and ulceration c. Increased incidence of secondary infections d. Generalized angioedema e. Increased pruritus 7. Which of these drugs has the weakest evidence for efficacy in treating atopic dermatitis? a. Doxepin b. Prednisone c. Cyclosporine d. Misoprostol e. Pentoxifylline 8. Which therapy is indicated for the initial treatment of a dog with mild seasonal atopic dermatitis of three months’ duration? a. Essential fatty acids and antihistamines b. Cyclosporine c. Injectable depot glucocorticoids d. Allergen-specific immunotherapy e. Misoprostol and prednisone 9. Which drug combination is thought to work synergistically in atopic dermatitis? a. Antihistamines and prednisone b. Pentoxifylline and misoprostol c. Fatty acids and topical antipruritics d. Cyclosporine and antihistamines e. Fatty acids and pentoxifylline 10. Disadvantages of cyclosporine use in dogs include: a. Frequent nephrotoxicity b. Expense c. Multiple doses per day d. Frequent hepatotoxicity e. Availability only in tablet formulation