Topical triamcinolone and allergic dermatitis: A case study

Galaxy, a 7-year-old intact male golden retriever, was presented on referral for evaluation of nonseasonal pruritus of four years' duration involving the feet, axillae,3ww ventral abdomen, and tailhead. The referring veterinarian had made a presumptive diagnosis of flea allergy dermatitis and had instituted flea control with fipronil, which alleviated the tailhead pruritus, as well as oral corticosteroid therapy, which was initially successful at controlling the remaining pruritus. However, during the previous year, prednisolone at a dose of 0.5 to 1 mg/kg orally daily had less effectively controlled the dog's clinical signs—the pruritus had intensified and the overall condition of the skin had worsened. In addition, Galaxy had developed polyuria, polydipsia, and a thin haircoat. The corticosteroid therapy was discontinued one week before presentation.

Figure 1A. Inguinal region: papular dermatitis due to bacterial folliculitis.

At referral, the owner reported that Galaxy was demonstrating moderate pruritus involving the inguinal area, feet, ears, dorsum, and flanks. Dermatologic examination showed a generalized papular to pustular dermatitis (Figure 1A), epidermal collarettes, a moderate to severe erythematous pododermatitis with excoriations and lichenification on all four feet (Figure 1B), hypotrichosis and inflammatory scaling on the trunk and tailhead (Figure 1C), and mild erythema and hyperpigmentation in the axillary and inguinal regions. The otic examination revealed bilateral ceruminous otitis externa with mild canal erythema and edema. No fleas or flea dirt was detected. The remaining physical examination findings were within normal limits.

Figure 1B. Pododermatitis: erythema, lichenification, and excoriations.

Differential diagnoses and primary workup

The differential diagnoses at this time included iatrogenic hyperadrenocorticism, flea allergy dermatitis (Galaxy's flea control had not been consistent), food allergy, atopic dermatitis, allergic otitis externa, secondary bacterial folliculitis, secondary Malassezia dermatitis, demodicosis, dermatophytosis, cheyletiellosis, and sarcoptic mange.

Figure 1C. Galaxy's dorsum: diffuse hypotrichosis and inflammatory scaling.

The initial workup included deep and superficial skin scrapings from multiple sites, fungal culture from affected abdominal skin, a complete blood count (CBC), serum chemistry profile, urinalysis, urine culture, serology for Sarcoptes antibodies, skin cytology from papules and pustules, and ear swab cytology.

Cytologic examination results showed numerous yeast consistent with Malassezia pododermatitis, neutrophilic dermatitis with intracellular cocci suggestive of bacterial folliculitis involving the inguinal region and dorsum (Figure 1D), and increased numbers of keratinocytes associated with numerous organisms consistent with Malassezia otitis (Figure 1E). The CBC, serum chemistry profile and urinalysis results were consistent with iatrogenic hyperadrenocorticism (moderately increased ALP and ALT activities and a urine specific gravity of 1.015); the urine culture was sterile. All other test results were within normal limits.

Figure 1D. Skin cytology from the inguinal area: inflammation with intracellular and extracellular cocci.

Updated differential diagnoses and initial treatment

Updated differential diagnoses at this time included allergic dermatitis (flea allergy, food allergy, and atopic dermatitis), bacterial folliculitis, Malassezia pododermatitis, allergic otitis externa with Malassezia infection, and iatrogenic hyperadrenocorticism.

The owner was informed that allergic dermatitis was the most likely underlying cause for the generalized pruritus and secondary skin and ear infections. Since the tailhead pruritus had previously improved with flea control, it was likely a result of flea allergy dermatitis. The owner was asked to improve flea control by treating all household animals. The cats were given fipronil combined with S-methoprene, and Galaxy was treated with biweekly imidacloprid. The dog's secondary bacterial folliculitis was treated with cephalexin at a dose of 25 mg/kg orally twice daily for four weeks.

Figure 1E. Ear cytology: keratinocytes with numerous extracellular yeast.

In addition, the owner was instructed to bathe the dog with a 2% chlorhexidine-2% miconazole shampoo once to twice weekly and use 2% acetic acid-2% boric acid wipes (Malacetic Wipes—DermaPet) once to twice daily on the interdigital areas. The ears were to be flushed twice weekly with a 2% acetic and 2% boric acid ear flush (Malacetic Otic—DermaPet) and an otic ointment containing prednisolone, polymyxin, and miconazole was to be applied to both ear canals.

Follow-up examinations and hypoallergenic diet trial

On reexamination three weeks later, the dog's skin had markedly improved but foot pruritus was still present. The dermatologic examination showed moderate postinflammatory scaling on the dorsum and trunk. Hypotrichosis had markedly improved. The axillary and inguinal skin was slightly inflamed and an erythematous pododermatitis was still evident. The otic examination findings were normal. Cytologic examination of samples from the feet showed only a few yeast. Because Galaxy had nonseasonal pruritus, the owner was advised to rule out food allergy dermatitis before pursuing intradermal skin testing.

A hypoallergenic diet containing a novel protein and carbohydrate source was started. Based on a comprehensive diet history of all previous foods, a commercial diet containing fish and potato was chosen. To alleviate pruritus, 0.015% triamcinolone acetonide topical solution (Genesis—Virbac) was prescribed twice daily for one week for use on all pruritic areas. During the second week, the spray was to be used once daily and thereafter every other day for an additional two weeks. The owner was instructed to wear gloves and to thoroughly saturate the affected areas.

Figure 2. Galaxy one year into therapy.

On reexamination four weeks later, the owner reported that Galaxy's pruritus was much improved. He was only rarely licking his feet, mainly on the days he was not being treated with the triamcinolone topical solution. The owner was asked to continue the hypoallergenic diet, to wipe the dog's feet as needed with the medicated wipes, and to try to decrease triamcinolone topical application to the lowest possible frequency. Shampoo therapy was reduced to every 10 to 14 days.

After the dog had received the diet for a total of eight weeks, his pruritus had markedly improved and the owner had decreased and then discontinued topical therapy except for occasional bathing. On reexamination, the dermatologic findings were normal. At this point the tentative diagnoses were food allergy and flea allergy, although atopic dermatitis had not been disproved. To help confirm a diagnosis of food allergy, the owner was asked to challenge Galaxy with his previous diet and monitor for any recurrence or worsening of clinical signs.

Four days later the owner reported an increase in Galaxy's pruritus. His hypoallergenic diet was reinstated and triamcinolone topical solution was used daily to alleviate pruritus. The pruritus improved within a few days and could be controlled with occasional shampoo therapy, medicated wipes, and triamcinolone topical solution applied once or twice weekly.

Two months later, Galaxy's pruritic dermatitis recurred despite his being fed the hypoallergenic diet. The relapse occurred with the arrival of spring. The results of an intradermal skin test showed multiple positive reactions to house dust and storage mites, molds, willow, birch, various grasses, mugwort, English plantain, nettle, and fleas. The dog was treated with allergen-specific immunotherapy. To alleviate Galaxy's pruritus until he responded to immunotherapy, topical therapy with triamcinolone topical solution, which had been discontinued about six weeks before the relapse, was reinstituted.

Diagnoses and outcome

Galaxy's final diagnoses were food allergy, atopic dermatitis, and flea allergy dermatitis. After about five months of allergen-specific immunotherapy combined with medicated wipes for the interdigital pododermatitis and triamcinolone topical solution to alleviate pruritus, both topical therapies were slowly decreased. Eight months after immunotherapy was initiated, all topical therapy was stopped. Over the next two years Galaxy's allergies were controlled with monthly allergen-specific immunotherapy, a fish and potato diet, and strict flea control (Figure 2). Intermittent concurrent topical therapy was necessary only during the summer months when grasses and weeds were pollinating.

Discussion of triamcinolone topical solution

Advantages. Triamcinolone topical solution offers several advantages over other topical corticosteroid products such as creams, lotions, and ointments. These products commonly contain hydrocortisone as their active ingredient. Triamcinolone is four to five times more potent than hydrocortisone and its spray formulation can be used on widespread areas and on haired skin.

Dose-dependent side effects. Galaxy showed signs of iatrogenic hyperadrenocorticism while receiving oral corticosteroid therapy. After treatment was switched to the topical triamcinolone, the clinical signs of hyperadrenocorticism resolved. The recommended protocol for triamcinolone topical solution usage suggests a decreasing dose over four weeks. Extralabel long-term use can be safe; however, regular reexaminations should be scheduled to identify potential side effects as early as possible. Continuous use on an as-needed basis can lead to severe side effects, the most common of which is cutaneous atrophy. Secondary skin infections, calcinosis cutis (Figure 3), and, with percutaneous systemic absorption, other signs of hyperadrenocorticism can also be observed. Particular caution should be used with cats and small dogs since smaller patients are more likely to experience systemic effects associated with topical corticosteroids. Owners should be carefully instructed on these potential side effects and how often and how long triamcinolone topical solution can be used in order to avoid them. Owners should also be made aware of the goals of therapy with any corticosteroid; use only the amount of medication required to alleviate discomfort and for as short a time as possible.

Figure 3. Local side effects of topical corticosteroids: inflammation and calcinosis cutis in a dog on long-term daily application of topical corticosteroids.

Use of triamcinolone topical solution in cats. Although it's extralabel, I have used triamcinolone topical solution with success in pruritic cats for atopic dermatitis or food allergies at a dose of once daily for one week and every other day for an additional one or two weeks. To prevent oral systemic absorption it is wise to have the cat wear an Elizabethan collar until the coat has fully dried. Side effects that may be seen in cats include local skin atrophy, floppy ears due to cartilage resorption and weakening, as well as skin fragility syndrome.

Conclusion

Taking a careful history is one of the most important steps when working up a pruritic animal. Before a diagnosis of allergic dermatitis can be made, all infectious causes must be identified and treated appropriately and flea and food allergies should be addressed. Allergy testing, both intradermal and serologic, is not a diagnostic tool. The results are used only to identify offending allergens and to prepare immunotherapy formulations. Good owner compliance is a mainstay in the successful management and long-term control of clinical signs in atopic patients.

This case study demonstrates that, if used judiciously and at the lowest effective dose, triamcinolone topical solution is an effective and safe alternative to systemically administered corticosteroids for long-term management of allergic dermatitis in dogs.