Volume 39 | Issue 1 Article 4

1977 Allergic Inhalent Dermatitis in the Canine Michael J. Frost Iowa State University

C. B. Chastain Iowa State University

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Recommended Citation Frost, Michael J. and Chastain, C. B. (1977) "Allergic Inhalent Dermatitis in the Canine," Iowa State University Veterinarian: Vol. 39 : Iss. 1 , Article 4. Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol39/iss1/4

This Article is brought to you for free and open access by the Journals at Iowa State University Digital Repository. It has been accepted for inclusion in Iowa State University Veterinarian by an authorized editor of Iowa State University Digital Repository. For more information, please contact [email protected]. Allergic Inhalent Dermatitis in the Canine by Michael J. Frost* c. B. Chastain, D.V.M., M.S.t

Summary A dog with allergic inhalant dermatitis Allergic inhalant dermatitis (AID) is but presents a diagnostic and therapeutic one of many causes of pruritus. Ecto­ challenge to the veterinarian. The patient parasites such as Cheyletiella and Sar­ exhibits intense pruritus often accompanied coptes should always be considered as by scratching, foot licking, face rubbing, possible causes of pruritus. Contact der­ sneezing, and lacrimation. The occurrence matitis or "prickle" dermatitis from soaps, of signs is often seasonal and is usually first synthetic rugs, rug cleaners, wool products seen in the second or third year. Allergic and straw are also common causes of inhalant dermatitis is an immediate type of pruritus. Bacterial skin infections allergic hypersensitivity mediated by the manifested as superficial pyoderma, skin sensitizing antigen, IgE. The allergen, folliculitis, furunculosis or associated with or sensitizing agent, usually pollen, mold or generalized demodectic mange are also dust, enters the body via inhalation. pruritic (10). Extensive and carefully taken Allergic inhalant dermatitis has a high history and routine as well as special tests hereditary tendency and may persist for the are necessary to differentiate AID from life of the patient. Diagnosis is based on other conditions. carefully taken history, results of in­ tradermal testing, and response to therapy. Discussion Allergic inhalant dermatitis can be con­ trolled by avoidance of the allergen, by AID is a form of atopy, a term coined by medical treatment, or by biological Coca and Sulzberger in 1922 to denote a treatment. It cannot be 'cured'. familial type of allergy. Atopy is an im­ mediate type of hypersensitivity or allergic Introduction reaction seen in man and lower animals. Approximately ten percent of humans are The veterinary clinician is often atopic and dogs are presumed to be presented with pruritic patients. In fact, similarly predisposed. The percentage of most dermatologic conditions are atopic dogs \vill increase since it is a highly characterized by scratching as the earliest inheritable condition. Chamberlain (9) clinical manifestation. All too often the estimates fifteen percent of the canine clinician is tempted to resort to cor­ population to be atopic and lists no par­ ticosteroid therapy in lieu of an orderly and ticular breed predispositions. Kirk and complete diagnostic workup. Cor­ Muller (14) list breed predilections for wire­ ticosteroids will frequently provide tem­ haired terriers, Dalmations, West Highland porary relief from the itching but unless the white terriers, and poodles. Lorenz (13) primary cause is uncovered and treated lists the Dalmation, wire-haired fox terrier, specifically, the patient will continue to itch Scottish terrier, Irish setter, and poodles. when taken off steroids or will suffer the The toy and terrier breeds seem most side effects or consequences of long term commonly affected but it has been reported corticosteroid therapy. in most purebred breeds as well as in mixed breeds. *M. Frost is a senior student in veterinary medicine, AID is only one of a number of allergic Iowa State University. tDr. Chastain is an Assistant Professor, College of diseases affecting the canine, but is unique Veterinary Medicine, Iowa State University. in that the allergen is inhaled and initiates

10 Iowa State University Veterinarian an immediate hypersensitivity reaction causes antibody production and sen­ manifested clinically as a dermatitis in the sitization of the animal. Upon subsequent dog. The antigen responsible for the exposure, the allergen reacts with the allergic state is a protein with a molecular specific antibody to cause the allergic weight of 10,000 or greater. The antigen reaction. An allergic dog seems may be seasonal, including pollens of predisposed to develop allergies to things grasses, trees, flowers, weeds and which are present in his environment for a ragweed, or nonseasonal such as long time. The reaction may be seasonal at housedust, kapok, feathers, wool, and first, but as the patient ages and adds new animal danders. The antibody responsible allergies to the existing ones, the disease for the allergic reaction belongs to the IgE may progress to a continuous affliction class of immunoglobulins and is known as which makes diagnosis more difficult (14). reagin or skin sensitizing antibody. IgE is a Probably the single most important homocytotropic antibody manufactured by aspect of making an accurate diagnosis in plasma cells and bound to circulating an allergic patient is an accurate history. basophils and tissue mast cells. The Question the client about onset of itching, homocytotropic antibody has a special when it is worst, previous medications, and affinity for the skin, i. e.} skin is the target response to treatment. Inquire about the organ or "shock tissue". The respiratory patient's diet and environment, especially system and the gastric mucosa may be where he sleeps. Also find out if the owners secondary target organs in the canine themselves or any other pets itch. Ragweed allergic reaction. When the cell bound allergy in the dog was first described in antibody comes in contact with circulating 1959 by Patterson (15). antigen it causes degranulation of the mast Ragweed and other pollenoses have been cells and liberation of vasoactive amines documented by many individuals since such as histamine, serotonin, kinins and then. The National Pollen Calendar is Slow Reactive Substance (SRS), heparin, published in several texts (9,14) and and proteolytic enzymes. These in turn regional pollen guides are available from cause smooth muscle contraction, Hollister-Stier Laboratories or Center capillary dilatation, and increased Laboratories. Weekly and daily pollen capillary permeability. The clinical signs of counts are posted locally and are valuable allergy develop immediately after this in correlating the onset of pruritus with the reaction occurs and are due to the effects of pollenation of various plants. Nonseasonal the vasoactive amines and proteolytic or perennially pruritic patients are more enzymes. The early signs are edema, likely to be hypersensitive to an allergen erythema, and pruritus. The areas most found indoors such as house dust, feathers, frequently involved with swelling, redness, kapok, wool, or any materials from which and itchiness are the feet (especially household furnishings are made. If the between the toes), around the eyes, the itching starts early in the spring before ears, the groin, and the perineal area. pollenation of plants, then molds should be Secondary excoriations may be seen from suspected as the allergen. The regional scratching the chest, ears, and axillae. fauna of molds varies considerably and the Chronic paw licking may lead to reddish species indigenous to Iowa may not be discoloration of the feet in white dogs. found in other states. Mites found in house Hyperhydrosis may accompany and dust, such as Dermatophagoides spp., have enhance the itchiness and paw licking. been shown to be allergenic in the dog (9). Conjunctivitis, epiphora, blepharitis and Multiple allergies develop as the dog ages otitis are frequently observed. The signs and leads to a perennial pruritus with may commen~e within ten minutes after seasonal exacerbations (14). exposure to the allergen (15), and continue Once a tentative diagnosis of allergic until the allergen is removed from the dog's inhalant dermatitis has been made, allergy environment. - testing may be employed to confirm the For an individual to develop hyper­ diagnosis and determine the allergens sensitivity, previous exposure to the responsible. Allergy testing by itself does allergen is ess-ential. The initial exposure not provide a diagnosis, but must be

Issue No.1, -1977 11 correlated with clinical signs and history. 7. Mixed epidermals (feathers, wool, and The optimal time for allergy testing is when horse, dog, and cat epidermals) the IgE, or reaginic antibody is at the 8. Extract of house dust highest concentration in tissues and clinical 9. Saline control signs are most severe. Prior to testing, the -inflammation and excoriations from These antigens were selected because they scratching should be controlled so the test are indigenous to central Iowa. They were areas are free of irritation. This must be obtained from Center Laboratories, Inc., accomplished without the use of either Port Washington, New York. A con­ corticosteroids or antihistamines. Soaking centration of 1000 protein-nitrogen units baths of tar or colloidal oatmeal are often (PNU) per ml is used for scratch testing; beneficial (10). All immunosuppressive 0.05 ml is used for each test. The technique drugs , tranquilizers, phenothiazine for testing has been described by Chastain derivatives, theophylline, atropine, and (10). It must be emphasized that a sympathomimetic amines should be diagnosis of AID is not made on the results withheld for- at least ten days. If possible, of skin testing alone. Clinically normal dogs no anesthesia or sedative should be used will react to the allergens with or without but meperidine hydrochloride (Demerol® previous exposure. Skin testing is used Winthrop), thiamylal, or a short-acting after the diagnosis is made in order to anesthetic may be used if the patient is demonstrate the specific allergens uncooperative. responsible for the clinical signs. There are several methods described that Interpretation of the results of in­ may be used to test for allergic reactions. tradermal and scratch tests must be The method used may depend upon the correlated with the history and physical areas involved, the severity of the con­ examination since hypersensitivities may dition, the sensitivity of the patient, and the coexist with other causes of pruritus. If the clinician's preference. The a vailable dog itched only in the spring but reacted 'methods are: only to ragweed pollen, the results would 1. Intradermal testing not be valid, since ragweed pollenates only 2. P-K (Prausnitz-Kustner) in August and September. Positive reac­ 3. Scratch test tions indicate present, past, or future 4. Pin prick test clinical hypersensitivities, cross reactions 5. Modified prick test with a similar antigen, excess concentration 6. Conjunctival test of test antigen, subclinical hypersensitivity, 7. Nasal and conjunctival smears contamination of the test antigen, or 8. Patch test dermographia "(extremely sensitive skin). 9. Provocative exposure Allergic inhalant' dermatitis can be Properly performed, the intradermal controlled by avoidance of the allergens, by technique is the most reliable and medical treatment, and by biological reproducible of all the SKIn testing treatment. When multiple allergens are techniques used. It has the disadvantage of involved, treatment is difficult. being technically the most difficult, but has The most effective way to control allergic the advantages of good quantitative and conditions encou·ntered in small animal qualitative control and is more easily read. practice is by preyenting exposure of the The antigens commonly used at the ISU animal to the substance which provokes the Teaching Hospital for intradermal and allergic state (9). For example, if ragweed scratch testing are: pollen is shown to be the allergen, the client is instructed to keep the patient indoors, 1. Mixed tree pollen extract preferrably in airconditioning or in an 2. Mixed grass pollen extract electrostatically filtered environment, 3. Tall and short Ragweed pollen extract during the pollen season of August and 4. Mixed weed pollen extract September, to keep the patient out of fields 5. Mixed mold extract where ragweed grows, or move to a non­ 6. Inhalants (orris root, silk, kapok, pollen area during the height of the pyrethrins) ragweed season. These last two suggesions

12 Iowa State University Veterinarian are hardly feasible since ragweed grows in released from mast cells following an all 50 United States, Mexico, and Canada. antigen-antibody reaction. The free Ragweed is a prolific pollen producer with histamine interacts with histamine each plant estimated to produce one billion receptors to exert its effects; these can be grains and one square mile producing blocked by antihistamines. But histamine sixteen tons of pollen. It is highly airborne release is a very minor part of the der­ and detected at altitudes exceeding 10,000 matological manifestations of AID and feet; pollen counts in large cities, miles antihistamines are reported to bring very· from the nearest.plant, are very high during negligible results (1, 11). However, some the pollen season. A permanent change of antihistamines have other pharmacological location does not greatly help the patient effects, such as central nervous system with multiple pollenoses since he soon depression and sedation, which may have develops sensitivities to allergens in the some benefit in reducing the urge to itch. new location and after a temporary im­ They may be beneficial in reducing the self provement will relapse. mutilation induced by excessive scratching If the patient is allergic to wool, removal in some cases of extreme pruritus (9). of all wool carpeting, rugs, clothing, and Corticosteroids are definitely the most furniture from the home would be widely used group of drugs for the symp­ beneficial but rarely feasible. Or, as in the tomatic treatment of allergic diseases of case of dust allergy, keep the patient in one small animals. Although they are of proven room without furniture or drapes, with a efficacy for the management of AID and frequently mopped tiled floor, and filtered other allergic conditions, they must be used air. If an allergen such as feathers is with caution since their misuse may lead to responsible, then removal of all feather severe side effects, most notably iatrogenic pillows from the dog's environment would hyperadrenalcorticism. Although the exact alleviate the symptoms. mechanism of action in tissue is not known, Medical treatment is most popular and their anti-inflammatory effects are probably takes two routes: topical and systemic. of primary importance. The ability of the Since the primary comp,laint is pruritus, steroids to inhibit inflammation may in­ topical treatments are aimed at soothing volve a stabilization of cell membranes. and relieving the itch. Medicated baths This action would prevent the disruption of reduce the inflammation and clean the skin. lysosomes and prevent the release of in­ Colloidal baths such as colloidal oatmeal flammatory substances contained within are absorptive, cleaning, and antipruritic. these cellular organelles. This membrane Tar baths, wet dressings, and lotions are stabilizing effect may also be important in also antipruritic. It is not uncommon for inhibiting the disruption of mast c,ell animals with AID to develop secondary granules and the release of vasoactive contact sensitivities to various topical substances such as kinins and Slow medications (1) so care must be taken to Reactive Substance (SRS). Steroids also avoid overtreatment with lotions and baths. stabilize the membranes of blood vessels to For patients with very short or sparse hair prevent the increased capillary per­ coats, topical creams of 0.5 to 1.0% meability and edema. In addition, steroids hydrocortisone acetate may be effective, decrease the synthesis of skin sensitizing but application of creams to dogs has antibody, IgE, by plasma cells. obvious drawbacks. The type of corticosteroid and the dosage Three types of drugs have been used must be selected to meet the needs of the systemically to treat AID. Tranquilizers individual patient. Repositol cortico~teroids may reduce the urge to itch but only should neft be used i.n the long term sedation will eliminate the itching so these management of pruritus. An effort should should be avoided. be made to find the lowest dose that will Antihistamines have long been used in alleviate the itching; the dosage will vary man for the control of allergic diseases but with the individual, the environment, and their value in the canine is extremely the season. A daily divided dose of about limited. The rationale is based on the belief 0.25 to 0.50 mg per lb. for forty to sixty days that the vasoactive amine histamine is will usually be adequate for a seasonal

Issue No.1, 1977 13 pollenosis (13), such as ragweed hyper­ injections. Alum precipitated extracts such sensitivity. If the pruritus is present for as Allypral® (Dome Labs, West Haven, longer periods, alternate day dosages or Conn.), a pyridine extracted aqueous regimens of three days on and three days antigen suspended in saline, require only 8­ off are effective. These regimens of therapy 10 injections. The large particle size and minimize the chance of adverse side effects relatively slow rate of absorption provide even when used for years (14), but periodic for prolonged stimulation of the immune check-ups and white blood cell differentials system. Therapeutically effective dosage to monitor the patient are recommended. levels can therefore be attained with fewer Prednisolone, prednisone, and hydrocor­ doses. A third type of vehicle is repository, tisone are used routinely. Repeated such as mineral oil, but is not advisable communication with the client is essential because of the possiblility of abscess in order to adjust the dosage to eliminate formation. Aqueous extracts in propylene the pruritus. At the end of the allergy glycol are reported to be very effective (9). season the drug should slowly be tapered The dosage and injection schedule used off since abrupt withdrawal could lead to an will vary with the patient but is essentially exacerabation of the allergi

14 Iowa State University Veterinarian 9. Chamberlain, K. W., Baker, E., et. at.: Sym­ 13. Lorenz, M. D.: Allergic skin disease. Kirk's posium on allergy in small animal practice. Vet. Current Veterinary Therapy, V, Philadelphia, W. Clinics of No. Am., Philadelphia, W. B. Saunders B. Saunders Co., 1974. Co., 1974. 14. Muller, G. H., and Kirk, R. W.: Small Animal 10. Chastain, C. B.: A screening test for canine atopic Dermatology, 2nd Edition. Philadelphia, W. B. dermatitis. V. M. S. A. C., 70:1315-1319, 1975. Saunders Co., 1976. 11. Chastain, C. B.: A Medical Aspects Review 15. Patterson, R.: Ragweed allergy in the dog. J. Am. Outline of Small Animal Dermatology. Baton Vet. Med. Assn., 135:178-180, 1959. Rouge, Louisiana State University, 1976. 16. Patterson, R.: Laboratory models of reaginic 12. Halliwell, R. E. W.: The immunology of allergic allergy. Progr. Allergy, 13:332-407, 1969. skin disease. .J. Small Anim. Pract., 12:431-433, 1971.

Otitis Externa and Surgery

by Cheryl Hedlund* Dr. D. DeYoungt

Otitis is defined as an inflammation of around the external auditory meatus, a the ear. There are three recognized types of predisposition to various allergies or to otitis corresponding to inflammation in the those who enjoy being in the water and various parts of the ear. Otitis externa is an swimming. inflammatory disease of the external ear The most frequently seen ear problem in canal. An inflammatory disease of the dogs is otitis externa. It is most frequently middle ear is otitis media and of the inner seen in dogs from 1-2 years of age, but is ear is otitis interna. These three diseases common from 1-4 years (9). There is no can be seen alone, but if left untreated or apparent correlation of occurrence with sex, improperly treated, disease in one location relative humidity or month of the year, will lead to involvement in the other areas, although the highest number of cases are as they communicate. treated in the summer (9). The tendency to The number of otology cases greatly ignore dogs that scratch at their irritated exceeds the yearly number of cases in ears results in more chronic than acute ophthalmology, orthopedic surgery, cases being presented which are usually urology and neurology (13). Some dogs are bilateral. more prone to ear problems because of Etiology their heredity, including breed and The causes of otItIS externa are num­ anatomy, their environment and their erous but often go undiagnosed. Knowing activities. Breed susceptibility is difficult to the etiology speeds recovery because the accurately determine because of varying proper treatment can be used initially. breed popularity with location and time. Causes include foreign bodies, parasites, The most commonly afflicted breeds are trauma, allergic skin diseases, general poodles, Spaniels, Retrievers, German infections, bacteria and fungi. Shepherds and terriers (5). Predilection for Grass awns, bugs, dirt, matted hair, otitis is associated with pendulous ears, water and dried wax are foreign objects long hair on the pinna and hair within and commonly found in the ear canal. When the canal is occluded, a continuously moist, warm, dark chamber is created that is ideal *C. Hedlund is a senior student in veterinary medicine, Iowa State University. for bacterial propagation. Shed epithelium, tDr. DeYoung is an Associate Professor, College of cerumen and other debris, especially in an Veterinary Medicine, Iowa State University. ear canal filled with hair, are sources of

Issue No.1, 1977 15