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Immune-mediated type IV adverse drug reactions are idiosyncratic in nature, generally not related to the primary or secondary pharmacology of the drug. Due to their complex nature and rarity, these iatrogenic reactions are seldom predicted or encountered during preclinical/early clinical development stages, and often precipitate upon exposure to wider populations (i.e. phase III onwards). They confer a burden on the healthcare sector in both a clinical and financial sense presenting a severe impediment to the drug discovery and development process. Research over the past 50 years has improved our understanding of these reactions markedly as both in vitro and in vivo studies have placed the role of the immune system, in particular; drug-responsive T cells, firmly in the spotlight as the mediators of these reactions. Indeed, the role of different populations of T cells in adverse events and the interaction of drug molecules with HLA proteins expressed on the surface of antigen-presenting cells is of considerable interest. Herein, this review examines the pathways of immune-mediated adverse events including the various T cell subtypes implicated and the mechanisms of T cell activation. Additionally, we address the enigma of immunological tolerance and explore the role tolerance plays in determination of susceptibility to such adverse events even in individuals carrying immunogenic liabilities., (© 2022 The Authors. Clinical & Experimental Allergy published by John Wiley & Sons Ltd.)

The Standards of Care Committee of the British Society for Allergy and Clinical Immunology (BSACI) and a committee of experts and key stakeholders have developed this guideline for the evaluation and testing of patients with an unsubstantiated label of penicillin allergy. The guideline is intended for UK clinicians who are not trained in allergy or immunology, but who wish to develop a penicillin allergy de-labelling service for their patients. It is intended to supplement the BSACI 2015 guideline "Management of allergy to penicillin and other beta-lactams" and therefore does not detail the epidemiology or aetiology of penicillin allergy, as this is covered extensively in the 2015 guideline (1). The guideline is intended for use only in patients with a label of penicillin allergy and does not apply to other beta-lactam allergies. The recommendations include a checklist to identify patients at low risk of allergy and a framework for the conduct of drug provocation testing by non-allergists. There are separate sections for adults and paediatrics within the guideline, in recognition of the common differences in reported allergy history and likelihood of true allergy., (© 2022 John Wiley & Sons Ltd.)

Aim: Penicillin allergy accounts for the majority of all reported adverse drug reactions in adults and children. Foregoing first-line antibiotic therapy due to penicillin allergy label is associated with an increased prevalence of infections by resistant organisms and longer hospitalisation. Clinician awareness of allergy assessment, referral indications, management of allergy and anaphylaxis is therefore vital but globally lacking. We aim to assess the knowledge of penicillin allergy, assessment and management in Western Australian health professionals., Methods: An anonymous survey was distributed to pharmacists, nurses and physicians within Western Australian paediatric and adult Hospitals, Community and General Practice., Results: In total, 487/611 were completed and included in the statistical analysis. Only 62% (301/487) of respondents routinely assessed for patient medication allergies. Of those who assessed allergy, 9% (28/301) of respondents met the Australian standards for allergy assessment. Only 22% (106/487) of participants correctly cited all indications for management with adrenaline in anaphylaxis to antibiotics and 67% (197/292) of physicians rarely or never referred to an allergy service. Paediatric clinicians had an increased understanding of allergy assessment and anaphylaxis management. Recent penicillin allergy education within a 5-year period led to significant improvements in allergy knowledge., Conclusion: Overall, knowledge, assessment and management of penicillin allergies among practitioners in Western Australia are currently inadequate in adults and paediatric clinicians to provide safe and effective clinical care. The implementation of a targeted education program for WA health professionals is urgently required and is expected to improve clinician knowledge and aid standardised penicillin assessment (de-labelling) practices., (© 2022 The Authors. Journal of Paediatrics and Child Health published by John Wiley & Sons Australia, Ltd on behalf of Paediatrics and Child Health Division (The Royal Australasian College of Physicians).)

Background: Serum total tryptase has been shown to increase during acute allergic reactions (acute tryptase, T A ); however, few studies have investigated the values of T A or a combination of T A and baseline tryptase (T B ) to discriminate positive from negative testing in perioperative hypersensitivity reaction (POH) allergy work-up. The aim of this study was to determine the diagnostic performance of T A in order to differentiate positive from negative allergy testing suspected POH and analyse the diagnostic performance of serial tryptase levels using several formulas., Methods: All patients from the University hospital of Montpellier and Strasbourg, France, who presented with suspected POH and underwent complete drug allergy work-up between March 2011 and December 2019 with available T A and T B were included. Four formulas, including a change in T A  > 11 (F1), or >2 + 1.2 × T B (F2), or >3 + T B (F3), or >120%T B (F4), were applied., Results: One hundred and sixty-two patients were included, and 131 of them (80.8%) had Grade III or IV reactions. Ninety patients had positive allergy testing. The optimal cut-off value of T A to distinguish positive from negative allergy testing patients was 9.8 μg/L with an AUC of 0.817 (95% CI: 0.752-0.882, p < .001). The 93% PPV threshold for T A was 33 μg/L (95.8% specificity). Paired tryptase levels according to formulas F2 and F3 yielded the highest Youden index (0.54 and 0.53, respectively)., Conclusion: The optimal cut-off point for T A for distinguishing positive from negative allergy testing suspected POH was 9.8 μg/L. T A value of 33 μg/L was required to achieve >90% PPV., (© 2021 John Wiley & Sons Ltd.)

Aim: Penicillin allergy labels are frequently encountered in children and are associated with significant harms. Most children are falsely labelled and can safely tolerate a penicillin but delabelling strategies are underutilised and paediatric-specific resources are lacking. The aim of this study was to evaluate an allergy assessment tool for children in hospital., Methods: We evaluated a paediatric-adapted penicillin allergy assessment tool, using an online survey of clinicians in a tertiary paediatric hospital, with 10 hypothetical potential penicillin allergy or adverse reaction cases (including non-allergy reactions). For each case, respondents were asked to use the tool to assign a reaction phenotype and recommend management. We determined the tool's sensitivity, specificity and acceptability to end users., Results: We evaluated 30 complete survey responses from senior and junior medical staff, nurses and pharmacists. The tool's overall sensitivity was 80.7% (95% confidence interval (CI) 74.2-87.1%) for assigning the correct reaction phenotype and 85.3% (95% CI 79.4-91.3%) for appropriate management. The tool had high sensitivity for identifying immediate hypersensitivity reactions at 95.6% (95% CI 90.2-100%). Most respondents agreed or strongly agreed that they would use the tool in their practice (22/30, 73.3%)., Conclusion: This survey evaluated a paediatric-adapted penicillin allergy assessment tool in a tertiary paediatric hospital among multidisciplinary clinician groups. The tool performed well overall and had high safety in identifying immediate hypersensitivity reactions. Further research to support implementation of allergy assessment and delabelling programmes among children is required., (© 2021 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).)

Since the late nineties, evidence has accumulated that flow-assisted basophil activation test (BAT) might be an accessible and reliable method to explore the mechanisms governing basophil degranulation and diagnostic allowing correct prediction of the clinical outcome following exposure to the offending allergen(s) and cross-reactive structures for different IgE-dependent allergies and particular forms of autoimmune urticaria. Although the BAT offers many advantages over mediator release tests, it is left with some weaknesses that hinder a wider application. It is preferable to perform the BAT analysis within 4 h of collection, and the technique does not advance diagnosis in patients with non-responsive cells. Besides, the BAT is difficult to standardize mainly because of the difficulty to perform large batch analyses that might span over several days. This article reviews the status of flow cytometric mast cell activation test (MAT) using passively sensitized mast cells (MCs) with patients' sera or plasma (henceforth indicated as passive MAT; pMAT) using both MC lines and cultured MCs in the diagnosis of IgE-dependent allergies. In addition, this paper provides guidance for generating human MCs from peripheral blood CD34 + progenitor cells (PBCMCs) and correct interpretation of flow cytometric analyses of activated and/or degranulating cells. With the recent recognition of the mas-related G protein-coupled receptor X2 (MRGPRX2) occupation as a putative mechanism of immediate drug hypersensitivity reactions (IDHRs), we also speculate how direct activation of MCs (dMAT)-that is direct activation by MRGPRX2 agonists without prior passive sensitization-could advance paradigms for this novel endotype of IDHRs., (© 2021 John Wiley & Sons Ltd.)

COVID-19-related mortality in high-risk individuals is substantial and current treatment options are limited. There is convincing evidence that the COVID-19 vaccines reduce the severity of infection and prevent deaths. Three COVID-19 vaccines are approved in the United Kingdom with many more in development. There are limited data on the triggers and mechanisms of anaphylaxis to these vaccines. We review the potential allergenic compounds in the COVID-19 vaccines and describe an innovative allergy support model for the vaccination hubs that allows most patients with severe allergy be immunized. Finally, we propose a practical algorithm for the investigations of anaphylaxis to these vaccines., (© 2021 John Wiley & Sons Ltd.)

Over the last 10 years, the electronic medical record has redefined medical documentation, and physicians rely on accurate records to make clinical decisions. Penicillin allergy labels (PALs) are important pieces of the medical history that guide physicians in selecting specific antibiotic classes for the treatment of infectious diseases. However, most children labelled as penicillin-allergic do not have an IgE-mediated (immediate) allergic reaction to penicillin or its derivatives. In the absence of confirmatory penicillin allergy testing or additional history, these children receive alternative, often broad-spectrum and second-line, antibiotics. Addressing unconfirmed PALs requires an understanding of how and why labels get added to the electronic medical record. This viewpoint highlights the knowledge gaps in paediatric outpatient penicillin allergy labelling and proposes an acronym ('LABEL') that primary care providers and antimicrobial stewards can utilise when designing initiatives to address unconfirmed PALs in the community., (© 2021 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).)

Background: Polyethylene glycols (PEGs) are widely used as excipients in drugs, cosmetics and household products. Immediate-type allergy to PEGs including anaphylaxis is rare. The recent introduction of the mRNA-based COVID-19 vaccines has led to an increased focus on PEG as a possible culprit of allergic reactions to the vaccines. A low awareness of the allergenic potential of PEG among consumers, manufacturers and doctors leads to under-diagnosis and under-reporting of allergy to PEGs, putting patients at risk of repeated severe reactions., Objectives: To investigate clinical manifestations, time to diagnosis and impact of a PEG allergy diagnosis on the daily life of patients diagnosed with allergy to PEG from 2010 to 2019., Method: Ten patients diagnosed with allergy to PEG were included. Detailed clinical history was obtained, and allergy investigations had been performed at the time of diagnosis. All patients were contacted and asked to retrospectively complete a questionnaire about causes and impact on daily life of an allergy to PEG, scored on a likert scale (0-10) before and after diagnosis., Results: Eight patients had experienced at least one anaphylactic reaction requiring adrenaline treatment. Anaphylaxis was primarily caused by antibiotic/analgesic tablets, depot-steroids, antacids and laxatives. Seven patients reported repeated reactions before diagnosis (median 3, range 2-6). Median time from first reaction to diagnosis was 20 months (range 2-120). None of the patients experienced severe allergic reactions after the diagnosis. Median likert score of the impact on daily life before diagnosis was 7 compared with 4 after diagnosis., Conclusion and Clinical Relevance: The clinical manifestations of PEG allergy are often dramatic. Improved awareness about the clinical presentation and common culprits, clear product labelling and a standardized nomenclature is needed to ensure the timely diagnosis of PEG allergy to prevent repeated anaphylactic reactions with severe impact on patients' lives., (© 2021 John Wiley & Sons Ltd.)

Background: Children are often diagnosed with an antibiotic allergy, with little investigation to confirm whether it is a true allergy. Recent studies support the use of oral challenges to confirm antibiotic allergy. Yet, little is known about families' perceptions of these challenges, or experiences of living with a misdiagnosis, often for many years., Objective: To describe how families with a child previously labelled as "antibiotic allergic," but who has subsequently been delabelled, perceive the experience of misdiagnosis and subsequent delabelling., Methods: We performed semi-structured interviews with parents whose children had recently completed a graded oral challenge for antibiotic allergy. Interview transcripts were analysed concurrently, but independently, by two investigators, using content analysis., Results: A total of 15 parents (14 individual interviews; 1 mother-father dyad) participated. Children were, on average, 5.04 ± 4.5 years and were first diagnosed in infancy (mean age: 1.82 ± 1.48 years) subsequent to a rash (14/14; 100%), and commonly at a walk-in clinic (6/14; 42.9%). We identified four themes: (1) A red, raised rash results in a quick diagnosis despite a lack of testing, (2) sensitive care allays concerns, (3) delabelling brings relief, but also mystery and calls for proper diagnoses, and (4) quick diagnoses are reckless, but manageable through downward comparisons., Conclusion and Clinical Relevance: These findings underscore the importance of a careful physical examination and clinical history of the patient, but also an ongoing dialogue to support families, both of which would ideally begin at the time of initial investigation., (© 2020 The Authors. Clinical & Experimental Allergy published by John Wiley & Sons Ltd.)

Alpha-gal syndrome (AGS) describes a wide spectrum of hypersensitivity reactions mediated by specific IgE to the α-gal epitope (galactose-α-1,3-galactose) ubiquitously expressed on glycolipids/glycoproteins of most mammals. This fascinating new entity has completely changed the paradigms of allergy as allergic response is directed against an oligosaccharide and the reactions can be both immediate and delayed. They appear to be stimulated only by tick bites which induce production of α-gal specific IgE antibodies that lead to (at times fatal) hypersensitivity response. AGS is completely different to previously described anaphylaxis to tick saliva. It provides unique insight into the interplay between different arms of the immune system and the role of ectoparasites in the development of anaphylaxis to food and medication in patients at risk of tick bites including travellers. This review summarises recent advances in our understanding of its clinical presentation, pathomechanism and role of various tick species in the development of AGS., (© 2020 John Wiley & Sons Ltd.)

Amoxicillin is the most common antibiotic prescribed in children with increasing use over time. While up to 10% of children are labelled as amoxicillin allergic, most children can tolerate amoxicillin after allergy evaluation. It is well documented that the label of amoxicillin allergy in children is associated with adverse health outcomes such as antibiotic-resistant infections. However, it remains controversial how best to assess children for amoxicillin allergy. While in general it is recommended that skin testing be done prior to drug provocation test in the evaluation of amoxicillin allergy, there is increasing evidence that drug provocation testing could be done in lower risk children without skin testing prior. The goal of this article as a narrative review is to review the strengths and limitations of skin testing prior to drug provocation test in children who have a history of either immediate or non-immediate, reactions to amoxicillin., (© 2019 John Wiley & Sons Ltd.)

Background: Beta-lactams allergy is the most commonly reported drug allergy and constitutes an important health problem. We previously showed the pre-existence of a naïve CD4+ T cell repertoire for benzylpenicillin (BP) coupled to human serum albumin (HSA) but little is known about the naïve CD8+ T cell repertoire specific for BP., Objective: The purpose of this work was to identify naïve CD8+ T cells specific for BP and to explore mechanisms dictating their activation., Methods: Co-cultures were established with naïve CD8+ T cells and autologous dendritic cells (DCs) loaded with HSA-BP or free BP. T cells were restimulated once a week with autologous DCs loaded with HSA-BP or BP. The specific CD8+ T cell response was measured using an IFN-γ ELISpot assay., Results: When using free BP, we were able to detect a naïve CD8+ T cell repertoire for BP in the 6 out of 7 tested healthy donors. However, our results showed that HSA-BP was recognized by naïve CD8+ T cells in only one donor out of five tested healthy donors. Using free BP, we evidenced its binding to cellular proteins in DCs that was concentration dependent and was correlated with BP-specific CD8+ T cell activation. Moreover, the BP-specific CD8+ cell response was MHC class I-dependent and required intracellular processing and proteasome activity., Conclusion and Clinical Relevance: This work showed the existence of a naïve CD8+ T cell repertoire for BP when DCs were treated with free BP suggesting that patients could be immunized by haptenated peptides from cellular proteins generated in antigen-presenting cells., (© 2019 John Wiley & Sons Ltd.)

Aim: To determine if skin testing (ST) in addition to extended oral provocation challenge (OPC) is necessary for beta-lactam allergy verification in an Australian paediatric population., Methods: This was a retrospective study (176 children) that undertook assessments for beta-lactam allergy from 2006 to 2015 at a tertiary paediatric hospital. Patients either underwent direct OPC without ST or ST plus challenge if ST was negative., Results: The analysis included children with a history of varying rash types/severity as well as angioedema and reported anaphylaxis. A direct OPC was undertaken in 73 children. Three children reacted with one anaphylaxis. A total of 103 children underwent ST, with 13 children (12.6%) reacting. Of the 90 who subsequently proceeded to OPC, 4 reacted. A total of 132 children were given an extended oral course of the culprit antibiotic, to which 6 children reacted., Conclusions: A direct OPC with the culprit drug in Australian children can be safely performed, avoiding resource-intensive and painful ST. Our data demonstrate that a prior history of anaphylaxis does not necessarily predict IgE-mediated allergy, as detected by positive immediate ST or reactions to oral challenge. Such history should not detract from efforts to assess these children for antibiotic allergy. We suggest that extended courses of at least 5 days are important in paediatric antibiotic de-labelling as six children (4.5% of those who were prescribed the extended course) reacted in our study and even developed symptoms late in the extended course, from days 2 to 6., (© 2018 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).)

Background: An omalizumab treatment and a high maintenance venom dose may both help to prevent recurrent systemic allergic reactions (SAR) to venom immunotherapy (VIT). The effectiveness of this combination therapy, however, is unclear., Objective: We wanted to explore the possibility whether a temporary treatment with the anti-IgE antibody omalizumab combined with a VIT using an elevated maintenance dose of >100 μg venom may establish a permanent tolerance of maintenance VIT., Methods: For this retrospective case series, we scoured our institutional data base for patients who had had an insect venom allergy, and in whom it had not been possible to continue VIT because of repeated unstoppable SAR during maintenance VIT. Patients were divided into those who had received the combination therapy (omalizumab group) and those who had not received omalizumab because its costs could not be covered (controls). Guided by the total IgE level and by body weight, omalizumab had been given subcutaneously 5, 3 and 1 weeks before VIT had been restarted. Three to 6 months after an elevated maintenance dose (200-300 μg venom) had been reached, omalizumab had been stopped., Results: Between 2006 and 2011, 15 patients had qualified for an off-label use of omalizumab: 10 patients had received the combination therapy, and 5 patients had remained without such a therapy. The combination therapy leads to a durable tolerance of VIT in all patients even after omalizumab had been discontinued (median of follow-up time 5.8 years, IQR 2.7-8.6 years). Sting challenge tests were tolerated by all of the re-stung omalizumab patients (n = 8). In all controls, VIT had to be stopped permanently due to repeated SARs (P < .001 vs omalizumab group)., Conclusions and Clinical Relevance: Combining a temporary omalizumab therapy with an elevated maintenance dose seems a promising approach to achieve a tolerance of treatment in patients with a recurrent SAR to VIT., (© 2017 John Wiley & Sons Ltd.)

Approximately 90-99% of patients with a label of penicillin allergy (PenA) are not allergic when comprehensively investigated. An inaccurate label of PenA has major public health implications-longer hospital stay, more frequent hospital admissions, greater use of fluoroquinolones, glycopeptides, cephalosporins and other expensive antibiotics resulting in significantly higher costs to the health service and predisposing to Clostridium difficile, methicillin-resistant Staphylococcus aureus infections and vancomycin-resistant enterococcus. We describe lessons learnt from recent studies regarding possible reasons contributing to an inaccurate label of PenA as well as propose a concerted multidisciplinary approach to address this important public health problem. Given the unmet need for allergy services in the UK and several other countries and knowledge gaps regarding PenA amongst healthcare professionals, we describe the potential role for a computerized clinical decision support system to enable non-specialists rapidly identify and de-label "low-risk" hospitalized patients with a label of PenA thereby obviating the need for allergy tests. This approach however needs rigorous evaluation for feasibility, safety, patient and physician acceptability, cost-effectiveness and its compatibility with information technology systems currently employed in the health service., (© 2017 John Wiley & Sons Ltd.)

Background: Guidelines for investigation of perioperative drug allergy exist, but the quality of services is unknown. Specialist perioperative anaphylaxis services were surveyed through the Royal College of Anaesthetists 6 th National Audit Project., Objectives: We compare self-declared UK practice in specialist perioperative allergy services with national recommendations., Methods: A SurveyMonkey™ questionnaire was distributed to providers of allergy services in the UK. Responses were assessed for adherence to the best practice recommendations of the British Society for Allergy and Clinical Immunology (BSACI), the Association of Anaesthetists of Great Britain and Ireland and the National Institute for Health and Care Excellence (NICE) Guidance on Drug Allergy-CG183., Results: Over 1200 patients were evaluated in 44 centres annually. Variation in workload, waiting times, access, staffing and diagnostic approach was noted. Paediatric centres had the longest routine waiting times (most wait >13 weeks) in contrast to adult centres (most wait <12 weeks). Service leads are allergists/immunologists (91%) or anaesthetists (7%). Potentially important differences were seen in: testing repertoire [10/44 (23%) lacked BSACI compliant neuromuscular blocking agent (NMBA) panels and 17/44 (39%) lacked a NAP6-defined extended panel; many failed to screen all cases for chlorhexidine 19/44 (43%) or latex 21/44 (48%)], staffing [only 26/44 (59%) had specialist nurses and 18/44 (41%) an anaesthetist] and provision of information [18/44 (41%) gave immediate information in clinic and 5/44 (11%) sign-posted support groups]. Most centres were able to provide diagnostic challenges to antibiotics [40/44 (91%]) and local anaesthetics [41/44 (93%)]., Conclusions and Clinical Relevance: Diagnostic testing is not harmonized, with marked variability in the NMBA panels used to identify safe alternatives. Chlorhexidine and latex are not part of routine testing in many centres. Poor access to services and patient information provision require attention. Harmonization of diagnostic approach is desirable, particularly with regard to a minimum NMBA panel for identification of safe alternatives., (© 2017 John Wiley & Sons Ltd.)

Background: Low-osmolar non-ionic radiocontrast media (RCMs) are commonly used throughout hospitals. However, the incidence of immediate adverse drug reactions (ADRs) to various low-osmolar non-ionic RCMs is not well studied. We compared the incidence of immediate ADRs among different low-osmolar non-ionic RCMs used in computed tomography (CT)., Methods: Severance Hospital has collected data for adverse reactions occurring in-hospital using an internally developed system. Using this data, we reviewed 1969 immediate ADRs from 286 087 RCM-contrasted CT examinations of 142 099 patients and compared the immediate ADRs of iobitridol, iohexol, iopamidol, and iopromide. We analysed the incidence of immediate ADRs to different RCMs, as well as the effect of single or multiple CT examinations per day., Results: Iopromide showed the highest incidence of immediate ADRs (1.03%) and was followed by iopamidol (0.67%), iohexol (0.64%), and iobitridol (0.34%). In cases of anaphylaxis, iopromide also showed the highest incidence (0.041%), followed by iopamidol (0.023%), iohexol (0.018%), and iobitridol (0.012%). Risk of immediate ADR due to multiple CT examinations (1.19%) was significantly higher than the risk due to a single CT examination (0.63%). Risk of anaphylaxis was also higher for multiple CT examinations (0.052%) than for a single CT examination (0.020%)., Conclusions and Clinical Relevance: The incidence of immediate ADRs varied according to the low-osmolar non-ionic RCM used. Iopromide-induced immediate ADRs were more frequent, while iobitridol was associated with fewer immediate ADRs than other RCMs. Multiple CT examinations per day resulted in a higher incidence of immediate ADRs and anaphylaxis than a single CT examination. Clinicians should consider these risk differences of immediate ADRs when prescribing contrasted CT examinations., (© 2016 The Authors. Clinical & Experimental Allergy Published by John Wiley & Sons Ltd.)

Background: Chlorhexidine is an effective disinfectant, which may cause severe allergic reactions. Plasma level of specific IgE to chlorhexidine (ImmunoCAP(®) ) has high estimated sensitivity and specificity when measured within 6 months of allergic reaction, but knowledge of the dynamics over longer time periods is lacking and it is unknown whether levels fall below <0.35 kUA/L in patients with previously elevated levels. It is also unclear whether re-exposure influences levels of specific IgE., Objective: To investigate the dynamics of specific IgE in chlorhexidine allergic patients with and without re-exposure., Methods: All patients diagnosed with chlorhexidine allergy in the Danish Anaesthesia Allergy Centre January 1999 to March 2015 were invited to participate. The study included blood samples from the time of reaction and time of investigation and blood samples drawn prospectively over several years., Results: Overall, 23 patients were included. Specific IgE within hours of reaction was available in eight patients and was >0.35 kUA/L in six of these. During allergy investigations, usually 2-4 months later, specific IgE was >0.35 kUA/L in 22 of 23 patients. In the following months/years specific IgE declined <0.35 kUA/L in 17 of 23 patients (most rapidly within 4 months). Nine re-exposures in the healthcare setting were reported by seven patients (35%). Most re-exposures caused symptoms and were followed by an increase in specific IgE. Two patients with specific IgE <0.35 kUA/L reacted upon re-exposure., Conclusions & Clinical Relevance: Time from reaction should be considered when interpreting specific IgE results. Specific IgE is >0.35 kUA/L in most patients at time of reaction but should be repeated after a few weeks/months if negative. The optimal sampling time seems to be >1 month and <4 months. A value <0.35 kUA/L neither excludes allergy nor implies loss of reactivity in previously sensitized patients. Re-exposures are common, often iatrogenic, and can cause a rebound in specific IgE., (© 2016 John Wiley & Sons Ltd.)

Background: Histamine H2 receptor antagonists are commonly prescribed medications and are known to be well tolerated. However, 99 cases of ranitidine-induced anaphylaxis occurred in Korea from 2007 to 2014., Objective: The purpose of this study was to determine the incidence, clinical features, and diagnostic methods for ranitidine-induced anaphylaxis., Methods: Ranitidine-related pharmacovigilance data from 2007 to 2014 were reviewed. Adverse drug reactions with causal relationships were selected, and clinical manifestations, outcomes, and drug-related information were assessed. For further investigation, 8 years of pharmacovigilance data were collected at a single centre. Twenty-three patients participated in in vivo and in vitro studies. Skin tests, oral provocation tests, and laboratory tests were performed, including tests using other kinds of histamine H2 receptor antagonists., Results: Over 7 years, 584 patients suffered adverse reactions to ranitidine. The most common manifestation was cutaneous symptoms. Among them, 99 patients (17.0%) experienced anaphylaxis. In a single-centre study, skin prick tests were positive in 91.7% of ranitidine-induced anaphylaxis patients (11/12); the optimal concentration was 20 mg/mL. Detection of ranitidine-specific immunoglobulin E failed. Cimetidine and proton pump inhibitors showed no cross-reactivity with ranitidine based on the skin prick test, oral provocation test, or clinical determination. Surprisingly, 82.6% of patients reintroduced ranitidine and re-experienced the same adverse reactions because ranitidine was not considered the culprit drug., Conclusions and Clinical Relevance: Although ranitidine is known as a safe drug, it can also cause diverse adverse reactions, including anaphylaxis. This study demonstrates the need to pay attention to adverse reactions to ranitidine and consider ranitidine as a cause of anaphylaxis., (© 2016 John Wiley & Sons Ltd.)

Background: The diagnosis of HSR to iodinated contrast media (ICM) is challenging based on clinical history and skin tests., Objective: This study evaluates the negative predictive value (NPV) of skin tests and intravenous provocation test (IPT) with low-dose ICM in patients with suspected immediate hypersensitivity reaction (HSR) to ICM., Methods: Thirty-seven patients with suspected immediate hypersensitivity reaction to ICM were included retrospectively. Skin tests and a single-blind placebo-controlled intravenous provocation test (IPT) with low-dose iodinated contrast media (ICM) were performed., Results: Skin tests with ICM were positive in five cases (one skin prick test and five intradermal test). Thirty-six patients were challenged successfully by IPT, and only one patient had a positive challenge result, with a grade I reaction by the Ring and Messmer classification. Ten of 23 patients followed up by telephone were re-exposed to a negative tested ICM during radiologic examination; two experienced a grade I immediate reaction., Conclusions & Clinical Relevance: For immediate hypersensitivity reaction to ICM, the NPV for skin tests and IPT with low dose was 80% (95% CI 44-97%)., (© 2016 John Wiley & Sons Ltd.)

Background: Immunoglobulin E-mediated allergy to drugs and substances used during general anaesthesia as well as non-allergic drug hypersensitivity reactions may account for anaesthesia-induced anaphylaxis. As IgE-mediated anaphylaxis is a potentially life-threatening reaction, identification of the culprit allergen is essential to avoid anaphylaxis recurrence during subsequent general anaesthesia., Objective: To study whether preventive recommendations derived from allergy testing after intraoperative anaphylaxis were followed in subsequent general anaesthesia., Methods: Results of standardized allergy testing after anaesthesia-induced anaphylaxis and outcome of subsequent general anaesthesia were analysed retrospectively., Results: Fifty-three of 107 patients were diagnosed with IgE-mediated allergy to a drug or substance used during general anaesthesia, and 54 patients were test negative. Twenty-eight of 29 allergy patients tolerated subsequent general anaesthesia uneventfully. One patient with cefazolin allergy suffered from anaphylaxis recurrence due to accidental reapplication of cefazolin. Twenty-two of 24 test-negative patients tolerated subsequent general anaesthesia, whereas two patients again developed anaphylaxis despite pre-medication regimens., Conclusion and Clinical Relevance: Our results confirm the practical impact of allergy testing in general anaesthesia-induced anaphylaxis. By identification of the allergen, it is possible to avoid allergic anaphylaxis during subsequent anaesthesia. In most cases, recommended pre-medication seems to prevent the recurrence of non-allergic drug hypersensitivity reactions., (© 2015 John Wiley & Sons Ltd.)