RAST Inhibition Research Articles

Evaluation of Skin Reactivity during (Immuno-) Therapy. Validation of Methods for Estimation of Changes in Skin Reactivity and Correlation to Shock Organ Sensitivity

Background: Parallel line bioassay (PLBA) has been acknowledged to be the gold standard for estimation of changes in reactivity, e.g., in RAST and ELISA inhibition tests. Objective: To study correlations between two simple methods for evaluation of changes in skin prick test (δSPT), using the slope of the allergen dose response (drra) in relation to PLBA. Methods: Skin prick test data from two published immunotherapy trials were used. In a D. farinae trial we used duplicate tests with three fixed ten-fold concentrations and in a P. judaica trial three tenfold individually chosen allergen concentrations causing wheals of similar size to that of histamine dihydrochloride 10 mg/mL, tenfold lower and tenfold higher concentration. Evaluation of the δSPT by PLBA, and two simple methods were correlated. In the D. farinae trial δSPT was compared to the change of conjunctival threshold concentration. Results: The δSPT as measured by both the simple methods gave similar results to that of PLBA (p<0.001). The δSPT was around 30-fold, i.e., about 3% of the pre-treatment reactivity. The δSPT correlated with the δCPT threshold concentration. Conclusions: Estimation of the δSPT during therapy expressed as change in concentration using simple methods based on the slope of the drra correlated well to changes by PLBA and CPT and should therefore be used both in clinical research and in practice.

Latex-Fruit Anaphylaxis from Persimmon

Background: Despite rare reports of persimmon anaphylaxis, the association of persimmon with natural rubber latex is low or undetermined, and latex-fruit syndrome presenting with anaphylaxis caused by persimmon has not been reported. Methods: Allergy skin testing were performed for aeroallergens, persimmon and plant foods, including those implicated in the latex-fruit syndrome and local fruits. Results: Strongly positive prick by prick and skin prick tests reactions in response to persimmon fruit, plant foods with known cross-reactivity with latex and latex were demonstrated. Conclusion: Our patient showed strongly positive allergy skin testing in response to persimmon fruit, specific plant foods with reported cross-reactivity with latex and latex. Although specific IgE for persimmon fruit and RAST inhibition latex immunoCAP are not available in our country We observed strongly positive reactions selectively towards the particular plant foods that contain class I chitinases, B-1,3-gluconase, profilin and patatin-like protein. Furthermore persimmon contains profilin, a cross reactive allergen to natural rubber latex. Total IgE was high and an IgE-mediated reaction was confirmed by immediate reactions.

Allergen of the Month—White Bursage

Allergen of the Month—White Bursage

Protein modification by biotinylated amoxicillin: usefulness in studies on allergy towards beta‐lactams

Background Beta-lactam (BLs) antibiotics are among the drugs most frequently eliciting allergic reactions, thus posing an important clinical problem. Protein haptenation plays a key role in immunological reactions to BLs and this process is considered necessary for the activation of the immune system. Therefore, it is of interest to develop tools to monitor this process. We have synthesized a biotinylated amoxicillin derivative (AX-B) to be used in the characterization of protein haptenation by amoxicillin (AX). Methods AX-B was obtained binding a biotin moiety at the lateral chain of AX. The recognition of AX-B by IgE of allergic patients was analyzed by RAST inhibition. AX and AX-B were used for the in vitro modification of proteins in serum and in cell culture. Modified proteins were separated by SDS-PAGE and detected by Western blot using an anti-AX antibody (for AX-modification) or HRP-streptavidin (for AX-B-modification). Distribution of intracellular protein adducts with AX-B was analyzed by confocal microscopy. Results AX-B showed a chemical reactivity similar to AX and competition studies suggested that AX-B and AX can modify the same targets. AX and AX-B behaved similarly in RAST inhibition studies with sera of patients with nonselective allergy to BLs, whereas competition by AX-B was poorer with sera of AX-selective patients. AX-B allowed the detection of protein adducts with high sensitivity. This derivative bound to all of the previously identified major AX targets in serum but made possible to detect some new targets. In addition, in cell culture, AX-B protein adducts could be detected intracellularly. Conclusions AX-B may constitute a valuable tool for the identification of AX targets with high sensitivity. The identity of novel AX-B targets will be the subject of future studies.

Study of Protein Haptenation by Amoxicillin Through the Use of a Biotinylated Antibiotic

Allergic reactions towards β-lactam antibiotics pose an important clinical problem. The ability of small molecules, such as a β-lactams, to bind covalently to proteins, in a process known as haptenation, is considered necessary for induction of a specific immunological response. Identification of the proteins modified by β-lactams and elucidation of the relevance of this process in allergic reactions requires sensitive tools. Here we describe the preparation and characterization of a biotinylated amoxicillin analog (AX-B) as a tool for the study of protein haptenation by amoxicillin (AX). AX-B, obtained by the inclusion of a biotin moiety at the lateral chain of AX, showed a chemical reactivity identical to AX. Covalent modification of proteins by AX-B was reduced by excess AX and vice versa, suggesting competition for binding to the same targets. From an immunological point of view, AX and AX-B behaved similarly in RAST inhibition studies with sera of patients with non-selective allergy towards β-lactams, whereas, as expected, competition by AX-B was poorer with sera of AX-selective patients, which recognize AX lateral chain. Use of AX-B followed by biotin detection allowed the observation of human serum albumin (HSA) modification by concentrations 100-fold lower that when using AX followed by immunological detection. Incubation of human serum with AX-B led to the haptenation of all of the previously identified major AX targets. In addition, some new targets could be detected. Interestingly, AX-B allowed the detection of intracellular protein adducts, which showed a cell type-specific pattern. This opens the possibility of following the formation and fate of AX-B adducts in cells. Thus, AX-B may constitute a valuable tool for the identification of AX targets with high sensitivity as well as for the elucidation of the mechanisms involved in allergy towards β-lactams.

Evaluation of the Effect of Pollution and Fungal Disease on Pinus radiata Pollen Allergenicity

Background: Pollutants and other stressing factors like mold infection might increase the production of pathogen-related proteins in plants. Since this is invoked as one of the causes for the high prevalence of allergic diseases in developed countries, we aimed to determine the potential effect of environmental pollution, with or without mold infection of the trees, on the allergenic potency of pine pollen (Pinus radiata). Methods: Pine pollen samples were recovered from three selected areas: low polluted (A), highly polluted (B) and highly polluted and infected with fungi (Spheropsis sapinea) (C). The allergenic potency of pollen from areas A, B or C were compared in vivo in 35 pine pollen-allergic patients by skin prick test and specific IgE (sIgE) quantification. Pollen was also analyzed in vitro by SDS-PAGE immunoblotting, RAST inhibition and cDNA-AFLP (amplified fragment length polymorphism) to compare differences in proteins and mRNA expression. Results: The allergenic potency measured by prick test, sIgE and RAST inhibition was greater in pollen A, which was exposed to smaller amounts of NO_x, PM₁₀ and SO₂ but greater amounts of O₃. No differences were found in IgE-binding bands in immunoblotting or densitometry of the bands. In cDNA-AFLP, three homologous transcript-derived fragments were expressed in samples B only, with an expressed sequence tag related with stress-regulated gene expression. Conclusions: A greater allergenic potency, in terms of skin tests and sIgE, is observed in pine pollen coming from unpolluted areas. We consider that this fact might be related to a higher exposure to ozone, resulting in a greater expression of allergenic proteins.

Allergy to natural rubber latex in asthma patients

Natural rubber latex (NRL) allergy has become an important occupational health problem in recent years. However, the prevalence of sensitization to NRL among allergic asthmatic patients is unknown. This study was undertaken evaluate the levels specific IgE in sera of 70 adult asthmatic patients (27 male and 43 female) with mild (32 patients) and moderate (38 patients) asthma, whose diagnosis was confirmed by case history, skin test results and RAST 20% of the asthmatics (14 patients) had latex-specific IgE in sera detected by Pharmacia UniCAP. Among the 14 latex sensitized asthmatics 6 patients had mild asthma and 8 had moderate asthma, 10 being male and 4 female. No latex-specific IgE was found in sera of 10 healthy donors. Among the 14 latex-sensitized asthmatics, 12 (86%) had sensitization to house dust; 13 (93%) sensitization to trees; 11 (79%) sensitization to grasses; 11 (79%) sensitization to weeds; 4 (29%) sensitization to cat/dog. There are no correlation between sensitivity to latex determined by latex specific IgE in sera and occupation of these asthma patients. 12 patients among the latex-sensitized asthmatics (86%0 had banana-specific IgE. 50 (72%) of the asthma patients had high levels of total IgE and all latex-sensitized asthmatics had high levels of total IgE. Using a one point RAST inhibition assay employing 10mg/ml of Greer latex extract 50% RAST inhibition was obtained, confirming specificity of the anti-latex IgE in these asthmatics. This study demonstrated a relatively high prevalence (20%) of in vitro reactivity to NRL allergens among patients with asthma. The source of sensitization to latex in these patients remains to be determined.

Role of minor determinants of amoxicillin in the diagnosis of immediate allergic reactions to amoxicillin

Skin testing of subjects with immediate hypersensitivity to amoxicillin is performed using major and minor determinants of benzylpenicillin plus amoxicillin. However, sensitivity is not optimal, and other determinants need to be considered. We assessed the sensitivity of stable, well-characterized minor determinants of amoxicillin in subjects with immediate allergic reactions to amoxicillin to improve skin test sensitivity. Amoxicillin, amoxicilloic acid, and diketopiperazine were prepared and characterized by reverse-phase HPLC, tested in vivo by skin testing and in vitro by basophil activation test and RAST inhibition assay. Patients with immediate hypersensitivity to amoxicillin were selected: Group A (n = 32), skin test positive just to amoxicillin; Group B (n = 19), skin test positive to benzylpenicillin determinants; Group C (n = 10), skin test negative and amoxicillin drug provocation test positive. In Group A, 27 subjects (81.8%) were skin test positive to amoxicillin, ten (30.3%) to amoxicilloic acid, two (6.1%) to diketopiperacine, and six (18.2%) negative. In Group B, nine (50%) were positive to amoxicillin, eight (42.1%) to amoxicilloic acid, none to diketopiperacine, and nine (50%) negative. In Group C, skin tests were negative. BAT was positive to amoxicillin in 26 patients (50.9%), to amoxicilloic acid in 15 (29.1%), and diketopiperazine in four (7.8%). RAST inhibition studies showed > 50% inhibition in all sera, with the highest concentration of amoxicillin and amoxicilloic acid. The combination of minor determinants of amoxicillin, amoxicilloic acid, and diketopiperazine seems to be of no greater value than the use of amoxicillin alone. Further efforts are needed to find new structures to improve sensitivity in the diagnosis of immediate hypersensitivity to betalactams.

IgE binding capacity of apple allergens preserved after high pressure treatment

Two strategies were performed to assay the antigenicity of an apple extract (Golden Delicious) after combined pressure/temperature treatments using pools of sera of patients with positive serum IgE to apple. The IgE binding capacity of SDS denatured proteins was tested after electro-transference to membranes. Additionally, competitive RAST inhibition tests were carried out with the native apple proteins. Antigenicity was also assessed after 10 months of storage. In general, the results with sera of Spanish patients obtained by the RAST inhibition method confirmed the negligible effects of high pressure treatments up to 800 MPa on apple antigenicity and IgE binding, similarly to other European populations. Immunoblots revealed, contrarily, that heat is more important than pressure in inducing irreversible changes in key epitopes. Furthermore, pressure treatments (up to 800 MPa) preserved inhibition scores in frozen apple extracts closer to the untreated controls during at least 10 months, which could be relevant in the design of strategies to preserve allergen antigenicity.

Dual sensitization to rat and mouse urinary allergens reflects cross‐reactive molecules rather than atopy

Sensitization to rats and mice can develop in laboratory animal workers exposed to only one species. Reasons for this dual sensitization are unclear but may reflect a genetic predisposition to developing allergy (atopy) or alternatively cross-reactivity between rat and mouse urinary allergens. We examined cross-reactivity between rat and mouse urine and the effect atopy has on dual sensitization in laboratory animal workers. In a cross-sectional study the frequency of sensitization to rat and/or mouse was analysed in 498 employees exposed to both rat and mouse at work and 220 to rat only. RAST inhibitions, western blots and blot inhibitions were carried out on a subset of five individuals to assess cross-reactivity. Fourteen per cent of workers were sensitized to rats and 9% to mouse. Over half (62%) of rat sensitized individuals were also mouse sensitized and the majority (91%) of mouse sensitized individuals were also rat sensitized. IgE cross-reactivity was demonstrated between rat and mouse urine using RAST inhibitions. Rates of atopy did not differ between rat only sensitized individuals compared with those sensitized to both species. Sensitization to cats and rabbits was more common amongst those with dual sensitization. Dual sensitization to rat and mouse reflects IgE cross-reactivity rather than atopy. Individuals with dual sensitization are more likely to be sensitized to other animal allergens. These findings will have implications for individuals working with only one rodent species who develop sensitization and symptoms to be aware of the potential for allergy to other species.

Allergie à Arundo donax. Une nouvelle observation chez un jeune clarinettiste

The authors report the case of a 10-year-old child with cheilitis due to a clarinet reed. It was a question of an allergy to giant reed ( Arundo donax), the antigen of which has recently been identified. Its molecular similarity to pollen allergens explains the association with pollinosis, as we observed in the present case. On the other hand, the onset of an allergy to a domestic wood does not have a clear explanation. The diagnosis was based on the history, prick tests, patch tests, serum-specific IgE assays and RAST inhibition. The lesion disappeared with avoidance.

The European Union CREATE Project: A model for international standardization of allergy diagnostics and vaccines

Allergen measurements are used extensively in the formulation of allergy diagnostics and vaccines, yet no purified international allergen standards are available for calibration purposes. The aims of the European Union CREATE project were to develop international standards with verifiable allergen content. Purified natural and recombinant allergens were analyzed by means of SDS-PAGE, mass spectrometry, circular dichroism spectra, and small-angle x-ray scattering. IgE reactivity was assessed by means of direct RAST, RAST inhibition, immunoblotting, and basophil histamine release with sera from 961 allergic patients. Three recombinant allergens, rBet v 1, rPhl p 5a, and rDer p 2, were structurally indistinguishable from their natural counterparts and showed excellent IgE reactivity suitable for use as certified reference materials. A second tier of allergens (rPhl p 5b, rOle e1, rDer p 1, rDer f 1, and rDer f 2) was identified that could provide suitable candidates for certified reference materials with minor improvements to the recombinant proteins. Only rPhl p 1 was considered unsuitable as a reference material. Quantitative ELISAs were identified that accurately measured each allergen, except for rPhl p 1. The CREATE project has provided a major step forward in allergen standardization and provides a model for the development of a comprehensive panel of international reference preparations that will harmonize allergen measurements worldwide.

Measurement of Lipid Transfer Protein in 88 Apple Cultivars

Background: Fruits are a major cause of food allergy in adults. Lipid transfer proteins (LTP) are implicated in severe allergic reactions to fruits, but little is known about LTP content in different cultivars. Objective: Determination of the levels of LTP in a wide range of apple cultivars. Methods: LTP was measured in apples from 53 cultivars grown in Italy and 35 grown in The Netherlands, using three different immunoassays: a competitive ELISA (cELISA), a sandwich ELISA (sELISA) and a RAST inhibition (RI). Selected cultivars were evaluated using the basophil histamine release test (BHR), skin prick test (SPT) and double-blind, placebo-controlled food challenge (DBPCFC). Results: LTP levels measured with the three immunoassays were significantly correlated, as judged by Pearson’s correlation (0.61 < Rp < 0.65; p < 0.0001), but differed with respect to the actual quantities: 3.4–253.2 (sELISA), 2.7–120.2 (cELISA) and 0.4–47.3 µg/g tissue (RI). Between cultivars, LTP titers varied over about a two-log range. Pilot in vitro and in vivo biological testing (BHR, SPT and DBPCFC) with selected cultivars supported the observed differences in LTP levels. Conclusions: Around 100-fold differences in LTP levels exist between apple cultivars. Whether the lowest observed levels of LTP warrant designation as hypo-allergenic requires more extensive confirmation by oral challenges. Determination of cultivar variation in LTP levels provides important information for growers and consumers. Comparison to earlier reported Mal d 1 levels in the same cultivars reveals that a designation as low allergenic does not always coincide for both allergens.

Limited IgE cross-reactivity between Dermatophagoides pteronyssinus and Glycyphagus domesticus in patients naturally exposed to both mite species

Contradictory results have been found when analyzing the IgE cross-reactivity among pyroglyphid mites and storage mites, as well as the role of these as true sensitizing agents. We sought to study the prevalence of sensitization to Glycyphagus domesticus in patients naturally exposed to this mite together with the more ubiquitous Dermatophagoides pteronyssinus and the IgE cross-reactivity between them. Mite species present in house dust samples of consecutive patients with mite allergy from Huelva (southwest Spain) were determined by means of light microscopy. Clinical sensitization was assessed by using skin prick and conjunctival provocation tests. Cross-reactivity at the IgE level was studied by using serum IgE determination and inhibition of RAST, IgE immunoblotting, and mite group 2 immunoassays. After D pteronyssinus, which is present in about 95% of house dust samples, G domesticus was the most important mite and present in about 50% of the samples. Tyrophagus putrescentiae and Lepidoglyphus destructor were detected in third and fourth place, respectively. About half of the patients with G domesticus at home were sensitized to this mite. A low IgE cross-reactivity was observed between D pteronyssinus and G domesticus, but an important IgE cross-reactivity was detected among glycyphagid mites at the level of group 2 allergens. Glycyphagid mites can act as primary sensitizing agents independently of pyroglyphid mites in a subset of patients naturally exposed to them. The inclusion of glycyphagid mite extracts in the diagnostic battery in areas with adequate mite growing conditions is important to ensure proper diagnosis.

Severe Immediate Allergic Reactions to Grapes: Part of a Lipid Transfer Protein-Associated Clinical Syndrome

Background: Grape allergy is considered rare; grape lipid transfer protein (LTP; Vit v 1), an endochitinase and a thaumatin-like protein (TLP) have been reported as grape allergens. A considerable number of patients have referred to our department for severe reactions to grapes, and several IgE binding proteins were detected. Objectives: The aim of this study was to identify and characterise the allergens involved in severe allergic reactions to grapes and describe the population in which they occur. Methods: Patients with reported severe allergic reactions to grapes (n = 37) are described. Grape allergens were purified/fractionated by a combination of chromatographic techniques, identified by proteomic analysis and biochemically characterised. Immunoreactivity was assessed by blot (inhibitions) and RAST (inhibitions), and skin prick tests were performed with the isolated allergens. Results: All subjects were polyallergic, sensitised and reactive to several additional foods and pollen. All patients were sensitised to grape LTP. A 28-kDa expansin, a 37.5-kDa polygalacturonase-inhibiting protein, a 39-kDa β-1,3-glucanase and a 60-kDa protein were identified as minor grape allergens. Endochitinase and TLP did not play a role. Inhibition experiments revealed the possible cross-reactive role of LTP for clinical sensitivities to other LTP-containing plant foods, but also the involvement of cross-reactive carbohydrate determinants of minor allergens in IgE cross-reactivity. Conclusions: LTP is the major grape allergen, while additional minor allergens may contribute to clinical reactivity. Severe grape allergy presents in atopic patients who frequently react to other LTP-containing, plant-derived foods. The ‘LTP syndrome’ is the appropriate term to describe this condition.

The role of profilin and lipid transfer protein in strawberry allergy in the Mediterranean area

In contrast to other Rosaceae fruit, only few cases of patients with adverse reactions to strawberry are listed in literature. OBJECTIVE To identify allergenic proteins in strawberry and to express and characterize recombinant strawberry lipid transfer protein (LTP; rFra a 3). Established apple-allergic patients were recruited on the basis of a reported allergic reaction to strawberry (n=28, confirmed by double-blind placebo-controlled food challenge in four patients) or on the basis of IgE reactivity to LTP (n=34). Sensitization to purified natural and recombinant allergens was assessed by RAST, immunoblot (inhibition) and basophil histamine release (BHR). A strawberry cDNA library was screened for genes homologous to known fruit allergens. Fra a 3 was cloned and expressed in the yeast Pichia pastoris and compared with peach and apple LTP by RAST, immunoblot-inhibition and BHR tests. Genes homologous to Bet v 1, Bet v 6, profilin and LTP were identified in a strawberry cDNA library. In BHR the rFra a 3 induced histamine release at a 100-fold higher concentration than peach LTP. RAST inhibition showed high cross-reactivity to peach and apple LTP, although IgE reactivity was lower by a factor 5. On strawberry immunoblot, patients' IgE showed reactivity to a Bet v 1 homologue, profilin, LTP and high-molecular weight bands. In addition to a Bet v 1 homologue, strawberry also contains IgE-binding profilin and LTP. The rFra a 3 has less allergenic potency than peach and apple LTP, and therefore is an interesting tool for future immunotherapy. Fra a 3 does not seem to be clinically relevant.

The Editors' Choice

The Editors' Choice

Immediate allergic reactions to cephalosporins: Evaluation of cross-reactivity with a panel of penicillins and cephalosporins

Allergy to cephalosporins has mainly been evaluated in the context of patients with confirmed penicillin allergy. The problem of studying cross-reactivity in subjects primarily sensitized to cephalosporins and potentially allergic to penicillins has not been sufficiently addressed. To evaluate the in vitro IgE response and cross-reactivity to betalactams in patients with immediate allergic reactions to cephalosporins. The study included 24 patients with immediate allergic reactions to cephalosporins and RAST-positive to at least 1 cephalosporin. Skin testing and RAST were performed with a panel of penicillins and cephalosporins. RAST inhibition assay with different monomeric conjugates of penicillin and cephalosporin was performed to establish cross-reactivity. The culprit cephalosporins were cefaclor (N = 7), cefonicid (N = 1), cefotaxime (N = 2), ceftazidime (N = 2), ceftriaxone (N = 3), and cefuroxime (N = 9). Two patients had a positive skin test result to penicillin determinants, and 22 patients had a negative result to penicillin determinants and tolerated benzylpenicillin administration. Of these 22, 19 had a positive skin test result to cephalosporins and divided into patients reacting only to the culprit cephalosporin (63.2%) and those reacting to more than 1 cephalosporin (36.8%). RAST and RAST inhibition studies confirmed that the side chain at the R1 position is crucial for recognition. The R1 side chain rather than the betalactam structure, shared by penicillins and cephalosporins, seems to play a dominant role in determining the specificity of immunologic reactions to cephalosporins. Thus, penicillin can be administered safely to patients allergic to cephalosporins and with a negative skin test result to penicillin determinants.

A mutant of the major apple allergen, Mal d 1, demonstrating hypo‐allergenicity in the target organ by double‐blind placebo‐controlled food challenge

Allergen-specific immunotherapy for food allergy has been hindered by severe side-effects in the past. Well-characterized hypo-allergenic recombinant food allergens potentially offer a safe solution. To demonstrate hypo-allergenicity of a mutated major food allergen from apple, Mal d 1, in vitro and in vivo. A mutant of the major apple allergen, Mal d 1, was obtained by site-directed mutagenesis exchanging five amino acid residues. Fourteen patients with combined birch pollen-related apple allergy were included in the study. Hypo-allergenicity of the mutant rMal d 1 (rMal d 1mut) compared with rMal d 1 was assessed by in vitro methods, i.e. RAST (inhibition), immunoblotting and basophil histamine release (BHR) and in vivo by skin prick test and double-blind placebo-controlled food challenge (DBPCFC). RAST analysis (n = 14) revealed that IgE reactivity to rMal d 1mut was twofold lower than that of the wild-type molecule (95% confidence interval (CI): 1.7-2.4). RAST inhibition (n = 6) showed a 7.8-fold decrease in IgE-binding potency (95% CI: 3.0-12.6). In contrast to this moderate decrease in IgE-binding potency, the biological activity of rMal d 1mut assessed by SPT and BHR decreased 10-200-fold. Hypo-allergenicity was confirmed by DBPCFC (n = 2) with both recombinant molecules. A moderate decrease in IgE-binding potency translates into a potent inhibition of biological activity. This is the first study that confirms by DBPCFC that a mutated recombinant major food allergen is clinically hypo-allergenic. This paves the way towards safer immunotherapy for the treatment of food-allergic patients.

Severe allergic reactions to guinea pig

BackgroundAllergic sensitization and reactions to guinea pig (Cavia porcellus) have been well documented in laboratory animal handlers, primarily manifesting as rhinitis, conjunctivitis, and asthma. Severe allergic reactions, however, are rare.MethodsWe report two patients with severe allergic reactions following non-occupational exposure to guinea pigs. The first patient, an 11-year-old female, developed ocular, nasal, skin and laryngeal edema symptoms immediately after handling a guinea pig. The second patient, a 24-year-old female, developed symptoms of isolated laryngeal edema after cleaning a guinea pig cage. Percutaneous skin testing, RAST, ELISA and ELISA inhibition testing with guinea pig extract were performed.ResultsBoth patients had IgE-mediated allergy to guinea pig confirmed by ELISA and either RAST or skin testing. ELISA inhibition studies confirmed the specificity of the IgE reactivity to guinea pig.ConclusionSevere IgE-mediated reactions can occur following non-occupational guinea pig exposure. Physicians should be aware of this possibility.