Intradermal allergy tests and specific allergen immunotherapy are still underutilized in the therapeutic management of feline dermatological conditions. This situation persists despite the demonstrated efficacy of these approaches in managing feline cutaneous atopic syndrome.
The retrospective multicenter study conducted by six specialized clinicians provides fundamental insight into the effectiveness of specific immunotherapy in reducing medication needs in felines with cutaneous atopic syndrome.
Methodology and Study Population
The investigation focuses on a cohort of 158 domestic felines presenting chronic or recurrent cutaneous manifestations evolving for at least one year. The studied population mainly comprises short-haired European cats (132 individuals), with a notable female predominance (92 females vs. 66 males). The median age is four years, with variations ranging from one to thirteen years.
Diagnostic Criteria for Feline Cutaneous Atopic Syndrome
Diagnosis relies on the identification of characteristic clinical patterns including self-induced alopecia (63 cases), cephalic and cervical pruritus (81 cases), eosinophilic granuloma complex lesions (50 cases), miliary dermatitis (18 cases), and diffuse pruritus (8 cases). More than a third of the animals simultaneously exhibit several clinical patterns, indicating the physiopathological complexity of this condition.
Severe feline eosinophilic granuloma
Establishing the diagnosis requires rigorous exclusion of other pruritic conditions. Exclusion protocols include an antiparasitic treatment of at least eight weeks to eliminate hypersensitivity to flea bites, an elimination diet using hydrolyzed proteins for a minimum of eight weeks, and the exclusion of bacterial or fungal infections through appropriate complementary examinations.
Intradermal Test Protocol
Intradermal tests are performed under sedation or general anesthesia, using pharmacological agents whose safety on skin reactions has been previously validated. The methodological innovation lies in the use of intravenous sodium fluorescein (5 mg/kg) in 136 animals, combined with examination under a Wood’s lamp to optimize the interpretation of skin reactions.
Allergen Panel and Concentrations
Tested allergen extracts include pollens (1/1000 w/v or 1000 NU/mL), dander (1/2000 w/v or 100 μg/mL), yeasts and molds (1/2000 w/v or 100 μg/mL), house dust and storage mites (1/2000 w/v or 100 NU/mL), and insects (1/2000 w/v or 1000 NU/mL). Each 0.05 mL injection is evaluated after 10 to 20 minutes according to precise criteria of erythema, size, and papular turgidity.
Positive reactions are defined by homogeneous fluorescence and well-demarcated papular contours, with a size equal to or greater than the average of the diameters of the negative and positive controls.
Allergy Test Results
The interpretability of the tests reaches 97% of the tested population (153 out of 158 felines). The absence of specific sensitization concerns 35% of the tested animals (53 cases), while 65% show positive reactions (100 cases). Among the latter, polysensitization largely predominates with 78 cases versus 22 monosensitizations.
Allergen Sensitization Profile
House dust mites represent the major allergen category with 74% of positive sensitizations. Dermatophagoides farinae is the predominant allergen (67% of positive cases), followed by Dermatophagoides pteronyssinus (27%). Storage mites affect 44% of sensitized animals, mainly Acarus siro (32%), Tyrophagus putrescentiae (27%), and Lepidoglyphus destructor (8%).
Pollen sensitizations affect 18% of cases for grasses, 19% for weeds, and 19% for tree pollens, respectively. Fleas induce positive reactions in 17% of the tested animals, while molds concern only 7% of the studied population.
Specific Immunotherapy Protocols
Specific immunotherapy is initiated in 78 of the 100 felines presenting sensitizations compatible with their anamnesis. Protocols use calcium phosphate or aluminum adjuvanted allergens, administered subcutaneously according to progressive dosage regimens. The number of allergens included varies from one to five per formulation, with an average of three allergens per treatment.
Allergen selection is based on intradermal test results and phylogenetic proximities, particularly for mites. Extracts containing proteases are not mixed with pollen extracts to avoid detrimental enzymatic interactions.
Evaluation of Therapeutic Efficacy
Medication Scoring System
Therapeutic efficacy is evaluated by a validated scoring system assigning points to different medication categories: antihistamines (10 points), corticosteroids depending on dosage (10 to 40 points), cyclosporine (5 to 30 points), and oclacitinib (10 to 40 points). A significant reduction is defined by a decrease of at least 30% in the medication score.
Comparative Results over Twelve Months
Forty-two felines treated with specific immunotherapy benefit from a complete twelve-month follow-up, compared to 36 untreated control animals. The groups show homogeneous epidemiological and clinical characteristics, validating the comparative relevance.
The initial medication score is significantly higher in the treated group (average 38 points, range 30-70) compared to the control group (33 points, range 10-60). This initial difference strengthens the robustness of the subsequent evaluation.
Evolution of Medication Needs
Specific immunotherapy generates a significant medication reduction in 74% of treated felines (31 out of 42 animals) with an average decrease of 58% from the initial score after twelve months (average final score: 16 points, range 0-40). In parallel, only 28% of control animals (10 out of 36) show spontaneous improvement with an average reduction of 19% (average final score: 27 points, range 0-50).
Kinetics of Therapeutic Improvement
Statistical differentiation between groups becomes significant after six months of treatment. Average reductions progressively stabilize at 13%, 38%, 43%, and 58% at 3, 6, 9, and 12 months respectively in the treated group, versus 5%, 9%, 10%, and 19% in the control group at the same time points.
Statistical analysis confirms the absence of correlation between the initial medication score and therapeutic response, suggesting efficacy independent of initial symptom severity.
Clinical Significance and Therapeutic Perspectives
This investigation constitutes the largest controlled study evaluating the efficacy of feline specific immunotherapy. The results demonstrate a statistically significant and clinically relevant medication-sparing effect, with complete treatment cessation in 26% of treated animals.
The use of intravenous fluorescein represents a safe methodological innovation optimizing the interpretation of intradermal tests, particularly for mite extracts traditionally difficult to evaluate.
The predominance of sensitizations to house dust and storage mites points towards targeted therapeutic strategies, while raising questions about cross-reactivity phenomena already documented in the canine species.
The limitations inherent to the retrospective nature of the study do not alter the robustness of the conclusions, given the protocol homogeneity among investigating centers and the statistical significance of the results obtained.
Brément T, Bensignor E, Drevon-Gaillot EV, Sanchez M-D, Pariente S, Viaud S. A retrospective, multicentric controlled study of the effect of specific allergen immunotherapy on medication needs in cats with atopic skin syndrome. Vet Dermatol. 2025;36:332–342.
