Common allergens of atopic dermatitis in dogs: comparative findings based on intradermal tests

Intradermal tests were performed on 58 dogs diagnosed with atopic dermatitis from 2004~2008 at the Veterinary Medical Teaching Hospital of Konkuk University, Korea. To compare the allergen distribution observed in the present investigation to the results from other studies conducted in Korea and elsewhere, the allergens were grouped according to their kinds. There was no significant difference in gender distribution among the dogs. The most common breeds among the 58 dogs were Maltese (n = 11) and Shih-tzu (n = 11). The average age was 4.8 years. The most frequently produced a positive reaction on the intradermal tests was mold (67.3%) followed by house dust (54.5%) and house dust mites (49.1%). The present study found a low distribution of dogs allergic to various outdoor allergens compared to studies performed in other countries; this may reflect differences in living conditions for dogs living in Korea.     

Effect of tiletamine/zolazepam sedation on intradermal allergy testing in atopic dogs.

Seven atopic dogs underwent intradermal allergy testing with 46 inhalant antigens before and after administration of a tiletamine/zolazepam solution (4 mg/kg of body weight, IV). This anesthetic protocol had no significant effect on the intradermal response caused by histamine, whole flea extract, or various inhalant allergens. Short-acting chemical restraint induced by the drug combination facilitated the intradermal testing procedure.     

Comparison of intradermal testing and serum testing for allergen-specific IgE using monoclonal IgE antibodies in 84 atopic dogs

OBJECTIVE: To compare an ELISA measuring serum allergen-specific IgE with intradermal skin testing in canine atopic dermatitis. PROCEDURE: Eighty-four dogs with the clinical diagnosis of atopic dermatitis underwent intradermal skin testing and serum testing for allergen-specific IgE. Tests were performed in a blinded fashion. Positive reactions were compared and the sensitivity and specificity of the serum test (using intradermal skin test as the standard) were determined overall and for individual allergen groups (grass pollens, weed pollens, tree pollens, house dust mites and fleas). RESULTS: The sensitivity of the ELISA overall was 90.4%. Evaluating the individual allergen groups, the sensitivity for dust mite hypersensitivity was 95.1%, for fleas 85.4%, for tree pollens 84.3%, for grass pollens 95.1% and for weed pollens 96.4%. The specificity was 91.6% overall, for dust mites 96.3%, for fleas 92.7%, for tree pollens 95.2%, for grass pollens 94% and for weed pollens 80.7%. CONCLUSION: The evaluated ELISA seemed reliable for the diagnosis of atopy in practice and can be recommended as a screening test prior to intradermal skin testing or for use in dogs when immunotherapy is not a therapeutic option.     

Late-phase reactions to intradermal testing with Dermatophagoides farinae in healthy dogs and dogs with house dust mite-induced atopic dermatitis

OBJECTIVE: To determine the prevalence of late-phase reactions to intradermal testing with Dermatophagoides farinae in healthy dogs and dogs with atopic dermatitis and an immediate reaction to D farinae. ANIMALS: 6 healthy dogs and 20 dogs with atopic dermatitis and immediate reactions to D farinae. PROCEDURE: ntradermal tests were performed with D farinae at 1:1,000 wt/vol and 1:50,000 wt/vol concentrations, and skin reactivity was evaluated after 0.25, 6, and 24 hours. Serum D farinae-specific IgE antibodies were assayed. Extent of lesions (atopy index) and pruritus (visual analogue scale) were evaluated in dogs with atopic dermatitis. RESULTS: Late-phase reactions were observed in healthy dogs at 6 hours (n = 2 dogs) and 24 hours (1) with the 1:1,000 wt/vol concentration, and at 6 hours (1) and 24 hours (1) with the 1:50,000 wt/vol concentration of allergen. Late-phase reactions in healthy dogs were only observed in dogs with an immediate reaction to D farinae. Late-phase reactions were observed in 11 of 20 dogs with atopic dermatitis at 6 and 24 hours with the 1:1,000 wt/vol concentration and in 10 of 20 at 6 and 24 hours with the 1:50,000 wt/vol concentration of allergen. There was no difference in mean atopy index, mean visual analogue scale of pruritus, or mean serum D farinae-specific IgE concentration of dogs with a late-phase reaction, compared to dogs without a late-phase reaction. CONCLUSIONS AND CLINICAL RELEVANCE: Late-phase reactions may be observed after an immediate reaction to intradermal skin testing in healthy and allergic dogs but are more commonly observed in dogs with atopic dermatitis.     

Evaluation of IgG subclass responses against Dermatophagoides farinae allergens in healthy and atopic dogs

A semiquantitative chemiluminescent Western blot analysis system was developed and validated to evaluate antigen-specific IgG subclass responses to electrophoretically separated proteins of Dermatophagoides farinae in healthy and atopic dogs. Both groups mounted similar D. farinae-specific IgG1 and IgG4 responses to multiple antigens, but IgG2 and IgG3 responses were difficult to detect. The most commonly recognized bands in both groups were 18 and 98 kDa antigens for IgG1 and 18, 45, 66, 98, 130 and 180 kDa for IgG4. The number of bands recognized per dog did not differ significantly, but significantly more atopic dogs had an IgG1 response to a 180 kDa protein. The overall D. farinae-specific IgG1 and IgG4 responses were slightly higher, but not significantly different, in the healthy group. The results suggest that some antigens produced by D. farinae can induce different subclass responses. However, as most of these responses are seen in both healthy and atopic dogs, they are likely to merely represent recognition of foreign proteins presented to the immune system, rather than involvement in the pathogenesis of atopic dermatitis. The role of the 180 kDa antigen warrants further study.     

Comparison of intradermal and serum testing for allergen-specific IgE using a Fcepsilon RIalpha-based assay in atopic dogs in the UK

Atopic dermatitis in dogs is a common allergic skin disease that affects substantial numbers of dogs in the UK. The purpose of this study was to compare the results of an intradermal test (IDT) and an in vitro test in a large cohort of dogs. Dogs were intradermal tested with Greer allergens (Greer Labs Inc, Lenoir, NC, USA) using standard techniques. At the same time blood samples were drawn and submitted for evaluation by ELISA using the ALLERCEPT Definitive Allergen Panels for allergen-specific IgE, a commercial assay that uses a biotinylated recombinant extracellular domain of the high affinity Fc-epsilon receptor alpha chain protein (Fcepsilon RIalpha). The allergens used in the two tests included grass, tree and weed pollens, moulds, flea saliva/whole flea extract and house dust mite species. The optical density readings from the ELISA for each allergen were compared with the results of the IDT for 265 dogs. The prevalence of positive reactions in the ELISA was equal to or greater than the results of the IDT in the case of almost all of the allergens, but two notable exceptions were the house dust mites Dermatophagoides farinae and Dermatophagoides pteronyssinus. These two allergens were the most common positive reactions by IDT (prevalence D. farinae 78.9%, D. pteronyssinus 66.4%). The results of the two tests were significantly different (McNemar's test, P<0.05) for 16 of the 22 allergens. The sensitivities of the ELISA compared to the IDT (where there were more than 3 dogs with positive reactions in both tests) varied between 19.3 and 77.1% (D. pteronyssinus 19.3% and D. farinae 67.9%) and the specificities varied between 64.2 and 96.6% (D. pteronyssinus 96.6% and D. farinae 89.3%).     

Effects of sedation on intradermal skin testing in flea-allergic dogs

Effects of 4 commonly used sedatives on the wheal-and-flare response to histamine and flea antigen were evaluated in 8 flea-allergic Beagles. Skin testing was performed in 12 separate occasions, 3 to 4 days apart. Twelve intradermal injections were given during each skin test: 5 doubling dilutions of histamine phosphate, 6 doubling dilutions of flea antigen, and a phosphate-buffered saline solution (negative control). Of the 12 intradermal skin tests, 8 were control tests performed on nonsedated dogs. The remaining 4 tests were performed on dogs sedated with xylazine, ketamine and valium combination, acepromazine, or oxymorphone. Oxymorphone had the most profound effect on skin test results, significantly (P less than 0.05) decreasing skin responsiveness in 8 of 11 test sites (by objective evaluation) and in 5 of 11 test sites (by subjective evaluation). Xylazine sedation enhanced skin test results in 4 of 11 test sites (by objective evaluation) and in 1 of 11 test sites (by subjective evaluation). In non instance did xylazine significantly decrease skin responsiveness to histamine or flea antigen. Xylazine is the recommended sedative in dogs when sedation is necessary for intradermal skin testing.     

Positive reactions to common allergens in 42 atopic dogs in Japan

Clinically important allergens for the diagnosis and treatment of atopic dermatitis vary geographically. In order to identify the most prevalent allergens in atopic dogs in Japan, 42 dogs with a clinical diagnosis of atopy were tested using both in vivo (intradermal skin test (IDST)) and in vitro (antigen-specific IgE assay) allergy tests. Allergens used for IDST included 26 allergen extracts from eight allergen groups: trees, weeds, grasses, house dust mites (HDM), molds, foods, epithelia, and arthropods. Immunodot assay was used to measure antigen-specific IgE against 24 allergens from these eight groups and against fish such as cod and sole. In the 42 dogs, the most common positive allergen reaction was to HDM on both IDST (29/42 dogs or 69%) and in vitro testing (23/42 or 54.8%). The second most frequent positive allergen reaction was to Japanese cedar pollen (21/42 or 50.0% for IDST and 7/42 or 16.7% for in vitro testing). In both tests, less than 20% of dogs had positive reactions to molds or foods. Positive reactions to cat epithelia were frequently found on IDST, but rarely found on in vitro testing. Agreement between the two tests was found in 26 instances: HDM (21 dogs), Japanese cedar pollen (five dogs) and wheat (one dog). In this study, the two most common allergens involved in atopic dermatitis in dogs in Japan were HDM and Japanese cedar pollen.     

Evaluation of an allergy screening test for use in atopic dogs.

An in-office allergy screening kit was evaluated for its repeatability, sensitivity, and specificity in 21 atopic dogs. Results of this testing were compared with results of a full regionalized allergy test offered by the same manufacturer. Results of the screening kit were repeatable and had high specificity but poor sensitivity. The kit as presently marketed is of questionable value as a diagnostic aid for use in dogs with atopy.     

Effects of otic betamethasone on intradermal testing in normal dogs

Otitis externa is common in atopic dogs and is frequently treated using potent glucocorticoids topically. These preparations can cause adrenal suppression and affect skin test reactivity. The purpose of this study was to determine if an otic product containing betamethasone could decrease skin reactivity in normal dogs. Sixteen laboratory beagles were used in a cross-over, blinded trial. Dogs were enrolled in two groups; one received placebo and the other a betamethasone-containing otic preparation (Otomax) twice daily for 2 weeks. After a 4-week wash-out period, treatments were switched. Dogs were intradermally tested on days 0 and 14 of each treatment period with histamine phosphate (1 : 100,000 and 1 : 200,000 w/v) and allergens common in the area. Adrenocorticotropic hormone (ACTH) stimulation tests were done before and after treatment to investigate adrenal suppression. After 2 weeks of otic betamethasone, Dermatophagoides farinae (P = 0.0034), Cynodon dactylon (P = 0.0459) and histamine 1 : 100,000 w/v (P = 0.0028) reactions were significantly reduced. Pre-treatment post-ACTH serum cortisol levels and those obtained after both treatments did not differ statistically (P = 0.6362). Betamethasone induced a slight but statistically significant elevation (P = 0.0002) of serum alkaline phosphatase. Despite the increase, values were within normal range. It is concluded that, although otic betamethasone did not suppress adrenal glands, it mildly suppressed intradermal reactions to 1 : 100,000 w/v histamine, D. farinae and C. dactylon.     

FC-50 Results of repeat intradermal testing in 135 dogs

Objective assessment of canine atopic dermatitis severity is very difficult and only a few scoring systems have been developed. The most commonly used is the Canine Atopic Dermatitis Extent and Severity Scoring Index (CADESI), adapted from the human SCORAD. Despite wide use of this score in clinical trials, no validation has been performed to our knowledge. The aim of this study was to determine the reliability of the CADESI in clinical practice. First, a set of 28 pictures taken from dogs diagnosed with atopic dermatitis was scored by six different investigators for three items: erythema, lichenification and excoriation. Next, 23 dogs with clinical signs compatible with atopic dermatitis were graded by two investigators using the CADESI. Erythema, lichenification and excoriation were assessed on 39 areas. With the pictures, significant correlations (Spearman's r , P  < 0.05) were found for each combination of investigators for erythema and lichenification, but only in 10 of 15 combinations for excoriation. Interobserver agreement ranged between poor and fair (0.221 < Cohen's κ <0.508, mean = 0.395). For the living animals, significant correlations ( P  < 0.0001), but poor interobserver agreement, were found for the three items (κ_erythema = 0.366, κ_{lichenification} = 0.385, and κ_excoration = 0.226). A significant correlation ( P  < 0.05) was found for each location, and interobserver agreement varied between very poor and good (0.16 < κ < 0.66). These results suggest that erythema and lichenification are reliably assessed, but that grading excoriation is more difficult. Also, the assessment of severity varied depending on the site studied.
Funding: Self-funded.     

Comparison between IMMUNODOT tests and the intradermal skin test in atopic dogs

This study evaluated a new perspective in the diagnosis of dermatitis in dogs with signs suggestive of allergic skin disease. The results obtained with CMG IMMUNODOT tests using the technique of allergen-specific strip tests, as employed for human allergy diagnosis, were compared with those obtained by the intradermal skin test (IDST). Forty-eight cases completed the diagnostic evaluation, which included IDST, flea-control program, exclusion of sarcoptes and, for some cases, a 1- to 2-month stabilization period on a restricted protein source diet and testing the serum in the presence of allergen-specific IgE and total IgE. The most common disorders included house and storage dust mites, allergic dermatitis and flea-allergic dermatitis together with atopy. This was confirmed serologically. In the case of positive IDST to pollens, Aspergillus spp. and cat epithelium, CMG IMMUNODOT strip tests were negative. A total of 25% of cases were considered to be primarily associated with food hypersensitivity, but only 4% were confirmed serologically. This study emphasizes the value of CMG IMMUNODOT tests as a support in the diagnosis of dog allergy.     

Effects of propofol-induced sedation on intradermal test reactions in dogs with atopic dermatitis

We compared the effect of propofol and saline control on intradermal test reactions in dogs with atopic dermatitis undergoing outpatient intradermal testing (IDT). Nineteen dogs were used in this clinical study. Patients were randomly allocated to receive either intravenous (IV) propofol or IV 0.9% saline, and IDT was performed on the right or left (randomized) lateral thorax. One investigator, unaware of the treatments, interpreted all IDT results. Injection sites were analysed using a subjective and objective method. A value of P or= 1+ on all dogs, significantly more positive sites were apparent during propofol sedation than during saline administration. In addition, the greater number of individual dogs experiencing more positive reactions >or= 1+ during propofol sedation was significant. When subjectively analysing reactions >or= 2+, the greater number of positive reactions and the greater number of dogs with more positive reactions observed during propofol treatment was not significantly different from the saline control. When analysed objectively, the greater number of positive reactions observed during propofol sedation was not significant. A greater number of dogs had higher subjective scores and larger objective measurements during propofol sedation compared with saline administration. In summary, propofol sedation was associated with an overall greater number of positive IDT reactions compared with the saline control. Although not always significant, this difference should be considered when choosing propofol for skin testing dogs with atopic dermatitis.     

The suitability of medetomidine sedation for intradermal skin testing in dogs

The objective of this study was to determine the suitability of medetomidine sedation for facilitating intradermal skin testing in dogs. Quality of sedation and immobilization, and effects of sedation on responses to intradermally injected histamine were evaluated. Ten clinically normal dogs were injected intradermally before and after medetomidine sedation (10 μg kg^?1 intravenously) with diminishing concentrations of histamine (100–10^?5μg mL^?1) and a negative control. Mean wheal responses at injection sites were compared before and during sedation, and no significant suppression of responses occurred during sedation. Medetomidine produced sedation that notably increased the ease of performing multiple intradermal injections in all dogs and sedative effects were rapidly reversed by the antagonist atipamezole. It was concluded that medetomidine may be an excellent sedative for facilitating intradermal skin testing in dogs provided further studies similarly reveal no inhibition of responses to intradermally injected allergens in atopic dogs.     

IgE reactivity and cross-reactivity to Japanese cedar (Cryptomeria japonica) and cypress (Chamaecyparis obtusa) pollen allergens in dogs with atopic dermatitis

The natural occurrence of Japanese cedar (Cryptomeria japonica) pollinosis has been reported in dogs with atopic dermatitis. However, the reactivity to Japanese cypress (Chamaecyparis obtusa) pollen allergens in these dogs has not been reported. The present study was designed to investigate the reactivity to Japanese cypress pollen allergens in dogs sensitized to Japanese cedar pollen allergens. In 19 dogs with specific IgE to C. japonica pollen allergen, we measured the specific IgE to C. obtusa pollen allergen and examined the reactivity to the allergen by intradermal test. Of the 19 dogs, 18 had specific IgE to crude and purified major allergens (Cha o 1) of C. obtusa pollen. Most of the dogs showed a positive reaction to C. obtusa pollen allergens in the intradermal test. Allergenic cross-reactivity between Cha o 1 and Cry j 1 (a major allergen in C. japonica pollen) was observed by the ELISA inhibition method. Dogs sensitized to Japanese cedar pollen allergens demonstrate reactivity to Japanese cypress pollen allergens.     

Stratum corneum removal facilitates experimental sensitization to mite allergens in atopic dogs

In humans with atopic dermatitis and in mouse models of IgE-mediated allergic diseases, evidence is mounting that the stratum corneum (SC) provides an important barrier against environmental allergens. At this time, it is not known whether the SC has a similar role in dogs, especially in those with atopic dermatitis. The objectives of this pilot study were to determine whether SC removal led to earlier and stronger sensitization of atopic dogs to Dermatophagoides farinae (Df) house dust mites. Five Maltese-beagle atopic (MBA) dogs were sensitized epicutaneously after the SC was removed with ten tape strips (TS group), while sensitization was done without tape strips in five other MBA dogs (nontape stripping; NTS group). During this 16 week study, sensitization was assessed with allergen-specific IgE serology, intradermal testing with Df allergens and determination of stimulation indices of blood mononuclear cells cultured with Df and stained for CD4 and the activation markers CD25 or CD30. Compared with dogs from the NTS group, those of the TS group exhibited earlier rises in Df-specific IgE serum levels, usually had higher allergen-specific IgE titres, showed higher intradermal test reactivity and had earlier increases and higher percentages of CD25- or CD30-positive activated allergen-specific peripheral CD4-positive T lymphocytes. These observations implicate a role of the SC as a barrier limiting sensitization to exogenous allergens in this experimental atopic dog model.     

Serum immunoglobulin E against storage mite allergens in dogs with atopic dermatitis

OBJECTIVE: To determine the prevalence of serum IgE against the storage mites Acarus siro, Blomia tropicalis, and Tyrophagus putrescentiae in a population of dogs with atopic dermatitis. SAMPLE POPULATION: Sera from 84 dogs with atopic dermatitis residing in various regions of the United States and Europe. PROCEDURE: Immunoblotting of sera from atopic dogs was used to identify proteins in mite extracts that bound IgE. RESULTS: 94% of the dogs had serum IgE against proteins in extracts of 1 or more of the storage mite species. Ninety-five, 92, and 89% of the storage mite-sensitive dogs had serum IgE against proteins in extracts of A siro, B tropicalis, and T putrescentiae, respectively. Eighty-two percent had serum IgE against at least 1 protein in all 3 species. Most of the major allergens had molecular weights > 80 kd. A greater percentage of the dog sera had IgE against storage mite proteins, compared with proteins of the house dust mites Dermatophagoides farinae and D pteronyssinus. CONCLUSION AND CLINICAL RELEVANCE: Many dogs with atopic dermatitis have serum IgE against many allergens of storage mites. Most of these allergens, like allergens of dust mites, had molecular weights > 80 kd. Storage mite sensitivity in dogs may be as important, if not more important, than dust mite sensitivity.     

Evaluation of intravenous fluorescein in intradermal allergy testing in psittacines

This study was designed to improve the clinical feasibility of intradermal skin testing of psittacine birds using intravenous fluorescein stain. Twenty-five healthy, anaesthetized Hispaniolan Amazon parrots (Amazona ventralis) were injected intravenously with 10 mg kg-1 fluorescein-sodium 1% followed by intradermal injections of 0.02 mL phosphate-buffered saline, histamine phosphate (1:100,000 w/v) and codeine phosphate (1:100,000 w/v) at the sternal apteria. Wheal diameters of reaction sites were measured grossly and under illumination with a Wood's lamp after 5 and 10 min. Fluorescence-enhanced injection sites were scored between 0 and 2, with 0 equivalent to normal skin and 2 equivalent to a plucked feather follicle. The presence of a fluorescent halo around intradermal injections was also recorded. Under Wood's light illumination at 10 min, histamine and saline were evaluated as positive and negative controls, respectively, based on a positive test having a halo and a score of 2. Sensitivity and specificity were each 76% for halo, 84 and 42% for score and 64 and 77% for combination of score and halo, respectively. Further, mean histamine reactions were significantly larger than codeine phosphate and saline (8.8 +/- 0.4 mm; 7.2 +/- 0.3 mm; 5.9 +/- 0.6 mm); however, this finding was not consistent in individual birds. Wheal size, halo presence and score were affected by site location independent from the injected compound. Intravenous fluorescein improved the readability of avian skin tests; however, the compounds tested raised inconsistent reactions in wheal size, score or halo presence. The compound-independent site effect raises concern on the validity of avian skin testing and warrants investigation of other techniques such as in vitro allergy testing. Based on our findings, intradermal allergy testing in psittacines with or without fluorescein is unreliable and cannot be recommended for practical clinical use.