PEG That Reaction: A Case Series of Allergy to Polyethylene Glycol.

Polyethylene glycol (PEG), also known as macrogol, is an excipient in numerous medications, health care products, cosmetics, and foods. It acts as an inert bulking, or stabilizing, agent. Despite its ubiquity, including in 2 of the newly launched vaccines against SARS-CoV-2, awareness of PEG allergy remains low. We present 6 cases of acute hypersensitivity to PEG. Accurate diagnoses in these cases posed a challenge, and although the triggering agents differed, PEG was demonstrated as the common culprit. All cases were female, with a mean age of 36.4 years. Four patients were originally suspected to have nonsteroid anti-inflammatory drug allergy, and 2 had a history of chronic spontaneous urticaria and angioedema. Biphasic allergic reactions featured prominently in this case series. Diagnosis relies on a high index of suspicion leading to a focused clinical history, supported by skin tests with PEG solutions to demonstrate sensitization. This case series highlights important clinical features of this rare, potentially serious, and increasingly recognized excipient allergy.

Eccema de los pies: oportunidad de las pruebas epicutáneas / Suitability of Patch Testing in Foot Eczema

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State-of-the-art and new options to assess T cell activation by skin sensitizers: Cosmetics Europe Workshop.

Significant progress has been made in the development and validation of non-animal test methods for skin sensitization assessment. At present, three of the four key events of the Adverse Outcome Pathway (AOP) are assessable by OECD-accepted in vitro methods. The fourth key event describes the immunological response in the draining lymph node where activated dendritic cells present major histocompatibility complex-bound chemically modified peptides to naive T cells, thereby priming the proliferation of antigen-specific T cells. Despite substantial efforts, modelling and assessing this adaptive immune response to sensitizers with in vitro T cell assays still represents a challenge. The Cosmetics Europe Skin Tolerance Task Force organized a workshop, bringing together academic researchers, method developers, industry representatives and regulatory stakeholders to review the scientific status of T cell-based assays, foster a mutual scientific understanding and conceive new options to assess T cell activation. Participants agreed that current T cell assays have come a long way in predicting immunogenicity, but that further investment and collaboration is required to simplify assays, optimize their sensitivity, better define human donor-to-donor variability and evaluate their value to predict sensitizer potency. Furthermore, the potential role of T cell assays in AOP-based testing strategies and subsequent safety assessment concepts for cosmetic ingredients was discussed. It was agreed that it is currently difficult to anticipate uses of T cell assay data for safety assessment and concluded that experience from case studies on real-life risk assessment scenarios is needed to further consider the usefulness of assessing the fourth AOP key event.

Atopic dermatitis in adults: a diagnostic challenge

Atopic dermatitis (AD) has a prevalence of 1%-3% in adults. Adult-onset AD has only been defined recently, and lack of familiarity with this condition and confusion regarding the appropriate terminology persist. AD may first appear in childhood or de novo in adults and is characterized by pronounced clinical heterogeneity. The disease often deviates from the classic pattern of flexural dermatitis, and there are forms of presentation that are specific to adults, such as head-and-neck dermatitis, chronic eczema of the hands, multiple areas of lichenification, or prurigo lesions. Although diagnosis is clinical, adult-onset AD frequently does not fit the traditional diagnostic criteria for the disease, which were developed for children. Thus, AD is often a diagnosis of exclusion, especially in de novo cases. Additional diagnostic tests, such as the patch test, prick test, skin biopsy, or blood test, are usually necessary to rule out other diseases or other types of eczema appearing concomitantly with AD. This article presents an update of the different forms of clinical presentation for AD in adults along with a proposed diagnostic approach, as new treatments will appear in the near future and many patients will not be able to benefit from them unless they are properly diagnosed (AU)

La dermatitis atópica (DA) en el adulto tiene una prevalencia del 1-3%. Es una entidad de reciente acuñamiento, que no todo el mundo conoce y sobre la que existe una gran confusión terminológica. Puede iniciarse en la infancia o presentarse de «novo» en el adulto. Presenta una gran heterogeneidad clínica y con frecuencia no sigue el patrón clásico de dermatitis flexural. Además, existen formas de presentación más propias de adulto como son la dermatitis de la cabeza y el cuello, eczema crónico de manos, áreas de liquenificación múltiple o lesiones de prurigo. Aunque su diagnóstico es clínico, muchas veces la DA del adulto no cumple los criterios diagnósticos «clásicos» de DA, pues están pensados para niños. Por eso, suele ser un diagnóstico de exclusión, sobre todo los casos de «novo». Suele precisar de la realización de pruebas diagnósticas para descartar otras enfermedades distintas u otro tipo de eczema sobreañadido a la DA. Las pruebas diagnósticas que pueden resultar útiles para ello son: pruebas epicutáneas, prick test, biopsia cutánea y una analítica sanguínea. Realizamos una actualización de las distintas formas de presentación clínica de la DA del adulto y establecemos unas pautas para llegar a su diagnóstico, pues en un futuro inmediato, con la aparición de nuevos tratamientos, muchos de estos pacientes no podrán beneficiarse de los mismos por no estar adecuadamente diagnosticados (AU)

State of the art in non-animal approaches for skin sensitization testing: from individual test methods towards testing strategies.

The hazard assessment of skin sensitizers relies mainly on animal testing, but much progress is made in the development, validation and regulatory acceptance and implementation of non-animal predictive approaches. In this review, we provide an update on the available computational tools and animal-free test methods for the prediction of skin sensitization hazard. These individual test methods address mostly one mechanistic step of the process of skin sensitization induction. The adverse outcome pathway (AOP) for skin sensitization describes the key events (KEs) that lead to skin sensitization. In our review, we have clustered the available test methods according to the KE they inform: the molecular initiating event (MIE/KE1)-protein binding, KE2-keratinocyte activation, KE3-dendritic cell activation and KE4-T cell activation and proliferation. In recent years, most progress has been made in the development and validation of in vitro assays that address KE2 and KE3. No standardized in vitro assays for T cell activation are available; thus, KE4 cannot be measured in vitro. Three non-animal test methods, addressing either the MIE, KE2 or KE3, are accepted as OECD test guidelines, and this has accelerated the development of integrated or defined approaches for testing and assessment (e.g. testing strategies). The majority of these approaches are mechanism-based, since they combine results from multiple test methods and/or computational tools that address different KEs of the AOP to estimate skin sensitization potential and sometimes potency. Other approaches are based on statistical tools. Until now, eleven different testing strategies have been published, the majority using the same individual information sources. Our review shows that some of the defined approaches to testing and assessment are able to accurately predict skin sensitization hazard, sometimes even more accurate than the currently used animal test. A few defined approaches are developed to provide an estimate of the potency sub-category of a skin sensitizer as well, but these approaches need further independent evaluation with a new dataset of chemicals. To conclude, this update shows that the field of non-animal approaches for skin sensitization has evolved greatly in recent years and that it is possible to predict skin sensitization hazard without animal testing.

La serie estándar en las pruebas alérgicas de contacto / The Spanish Standard Patch Test Series

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Prick test: evolution towards automated reading.

The prick test is one of the most common medical methods for diagnosing allergies, and it has been carried out in a similar and laborious manner over many decades. In an attempt to standardize the reading of the test, many researchers have tried to automate the process of measuring the allergic reactions found by developing systems and algorithms based on multiple technologies. This work reviews the techniques for automatic wheal measurement with the aim of pointing out their advantages and disadvantages and the progress in the field. Furthermore, it provides a classification scheme for the different technologies applied. The works discussed herein provide evidence that significant challenges still exist for the development of an automatic wheal measurement system that not only helps allergists in their medical practice but also allows for the standardization of the reading and data exchange. As such, the aim of the work was to serve as guideline for the development of a proper and feasible system.

Seasonal local allergic rhinitis in areas with high concentrations of grass pollen

Background: Local allergic rhinitis (LAR) is a phenotype of allergic rhinitis characterized by the presence of a localized immune response in the nasal mucosa of patients with negative skin prick test (SPT) results and undetectable serum specific IgE (sIgE). It unknown whether LAR is limited to areas with low or moderate aeroallergen exposure. Objective: To explore the presence of LAR and the clinical and immunological characteristics of this entity in geographic areas with high grass pollen loads. Methods: A cross-sectional observational study was carried out in 2 hospitals in central Spain (Madrid and Ciudad Real). Sixty-one patients with seasonal rhinitis and negative SPT results and undetectable serum sIgE were evaluated using a clinical questionnaire, determination of serum total IgE, and a nasal allergen provocation test (NAPT) with Phleum species. The response to NAPT was monitored using assessment of nasal symptoms, acoustic rhinometry, and determination of sIgE, tryptase, and eosinophil cationic protein in the nasal cavity. Results: Seasonal LAR was detected in 37 patients (61%) using the techniques described above. Eleven percent of patients with LAR were adolescents or children, and 14% reported onset of rhinitis in childhood. Most patients reported persistent-moderate seasonal nasal symptoms, and 41% reported worsening of the disease during the last 2 years. Conjunctivitis was the most common comorbidity, affecting 95% of cases. Conclusions: LAR to grass pollen is relevant in patients with seasonal symptoms indicative of allergic rhinitis but with a negative skin test result who live in areas with high allergenic pollen loads. This entity should be included the differential diagnosis of rhinitis (AU)

Introducción: La rinitis alérgica local (RAL) es un fenotipo de rinitis alérgica (RA) caracterizado por la presencia de una respuesta inmunológica localizada en la mucosa nasal de pacientes con pruebas cutáneas (PC) negativas e IgE específica (sIgE) sérica no detectable. Se desconoce si la RAL es una entidad limitada a áreas con baja o moderada exposición a aeroalérgenos. Objetivos: Explorar la presencia y características clínico-inmunológicas de la RAL en áreas geográficas con alta concentración atmosférica de polen de gramíneas. Métodos: Estudio observacional-transversal realizado en dos hospitales de la zona centro de España (Madrid y Ciudad Real). Sesenta y un pacientes con rinitis estacional, PC negativas y sIgE sérica no detectable fueron evaluados mediante cuestionario clínico, IgE total sérica, y test de provocación nasal con Phleum (TPN-Phleum). La respuesta al TPN se monitorizó mediante síntomas, rinometría acústica, y determinación de sIgE, triptasa y proteína catiónica de eosinófilos en secreciones nasales. Resultados: Se detectó RAL estacional en 37 pacientes (61%) mediante TPN-Phleum. El 11% de los pacientes eran adolescentes o niños, y el 14% habían comenzado con los síntomas en la infancia. La mayoría presentaban rinitis estacional persistente-moderada, y el 41% refirió empeoramiento en los 2 últimos años. La conjuntivitis fue la enfermedad asociada más frecuente, afectando al 95% de los sujetos con RAL. Conclusiones: La RAL por polen de gramíneas es una enfermedad frecuente en pacientes con síntomas indicativos de RA estacional y PC negativas que viven en áreas con alta concentración atmosférica de pólenes, y debe ser incluida en el diagnostico diferencial de la rinitis (AU)

Adaptación transcultural del cuestionario Urticaria Control Test del alemán al castellano / Cross-Cultural Adaptation of the Urticaria Control Test From German to Castilian Spanish

INTRODUCCIÓN: Bajo el concepto de urticaria se incluye un grupo heterogéneo de entidades clasificadas según su evolución en urticaria aguda (duración inferior a 6 semanas) y urticaria crónica (duración igual o superior a 6 semanas). Las formas crónicas incluyen la urticaria crónica espontánea y las urticarias inducibles. Disponemos de un número limitado de herramientas para la monitorización de las distintas formas clínicas de urticaria y para la valoración de su impacto en la calidad de vida. Recientemente se ha creado el cuestionario Urticaria Control Test como herramienta para valorar el control de la urticaria, disponible tanto en alemán, el idioma original, como en inglés americano. OBJETIVO: Realizar la adaptación transcultural al castellano de las versiones larga y corta del Urticaria Control Test garantizando su equivalencia con la versión original. MATERIAL Y MÉTODOS: Metodología de traducción directa, traducción inversa y entrevistas cognitivas siguiendo los principios de buena práctica de la International Society for Pharmacoeconomics and Outcomes Research. RESULTADOS: La primera versión del cuestionario en español, obtenida por traducción directa de la versión original, fue sometida a entrevistas cognitivas, realizándose modificaciones en 3 preguntas. Al valorar los autores originales la nueva versión obtenida por retrotraducción, se modificó únicamente una pregunta, ya que consideraron que con el cambio había perdido el enfoque global de la cuestión original. Se realizó una tercera versión, que fue sometida a mínimas modificaciones, obteniéndose la versión definitiva. CONCLUSIONES: Este trabajo facilita la utilización en castellano del cuestionario Urticaria Control Test en un paso previo a su validación

INTRODUCTION: The clinical concept of urticaria embraces a heterogeneous group of conditions classified according to their clinical course as acute (lasting less than 6 weeks) or chronic (lasting 6 weeks or more). Chronic urticaria may be either spontaneous or induced. Few tools are available for monitoring the various clinical forms of this disease or for evaluating its impact on quality of life. The recently developed Urticaria Control Test to evaluate disease control is available in German, the original language, and American English. OBJECTIVE: To culturally adapt the long and short versions of the Urticaria Control Test to Castilian Spanish to ensure equivalence between the translated items and those of the original version. MATERIAL AND METHODS: To translate the Urticaria Control Test we followed the International Society for Pharmacoeconomics and Outcomes Research good practice guidelines, starting with forward translation and moving through back translation and cognitive debriefing steps. RESULTS: Three items were modified when the first Spanish version, translated from German, was discussed (cognitive debriefing). The revised translation was then translated back to German and sent to the Urticaria Control Test authors, who modified one item they considered had acquired a different focus through translation. A third Spanish version was then prepared and after minor proofreading changes was considered definitive. CONCLUSIONS: This study was the first step in making it possible to use the Urticaria Control Test questionnaire in Castilian Spanish. The next step will be to validate the translated questionnaire

Factors associated with different results of allergy tests in children with dust mite-induced atopic dermatitis

BACKGROUND: Atopic dermatitis (AD) is a public health problem, with an increasing prevalence worldwide. AD is a chronic inflammatory disease characterised by skin lesions and severe itching. Immunologically, AD has two forms, IgE-mediated and cell-mediated, but it may also be idiopathic. In the pathogenesis of AD, the gene mutations for filaggrin, a filament-aggregating protein present in the epidermis, are of pivotal importance, but other genetic factors are also operating, including those linked to family atopy. METHODS: We evaluated the role of family atopy, and of the results of the atopy patch test (APT) in parents, in children with mite-induced AD. 64 children, 38 males and 26 females, mean age 4.97 years, were included for the diagnosis of AD and underwent APT and skin prick test (SPT) with dust mite extracts, with evaluation of atopy and result of APT also in parents. RESULTS: A positive family history of atopy was shown for children with positivity to both APT and SPT compared to those with negative or only one positive result to APT or SPT (p = 0.08). Significant associations were found concerning APT results in children and parents. In particular, children of a positive-APT parent had an 18-fold higher risk of APT-positivity in comparison with children of negative-APT parents, while the risk was 6.6-fold higher if APT was positive in father. CONCLUSION: Family atopy and a positive APT in fathers are risk factors to develop cell-mediated AD, as assessed by the APT, in children

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Allergy workup for suspected folic acid hypersensitivity

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Pruebas epicutáneas en pacientes con eczema perianal / Patch Testing in Patients With Perianal Eczema

INTRODUCCIÓN Y OBJETIVOS: La prevalencia de parches positivos en los pacientes afectados por una dermatitis anogenital oscila según las series entre un 25-78%, justificándose por tanto la realización de pruebas epicutáneas ante eczemas de esta localización. Los objetivos del presente estudio son por un lado determinar los alérgenos más frecuentes en los pacientes con eczema perianal y, por otro, establecer las baterías de alérgenos más útiles para el estudio con pruebas epicutáneas de esta afección. MATERIAL Y MÉTODOS: Se han revisado retrospectivamente (años 2001-2012) los resultados obtenidos al estudiar con pruebas epicutáneas a aquellos pacientes que presentaban exclusivamente un eczema perianal. RESULTADOS: De los 37 pacientes con esta clínica en 16 se observó alguna reacción positiva, siendo el metilcloroisotiazolinona/metilisotiazolinona el principal alérgeno implicado. Excepto un caso con sensibilización a gentamicina, todas las positividades con relevancia presente correspondieron a alérgenos de la batería estándar del Grupo Español de Investigación en Dermatitis de Contacto y Alergia Cutánea (GEIDAC) o a productos propios del paciente. CONCLUSIONES: En nuestra experiencia la metilcloroisotiazolinona/metilisotiazolinona es el principal alérgeno implicado en los eczemas perianales, procediendo esta sensibilización frecuentemente del uso de toallitas higiénicas. El estudio epicutáneo de un eczema perianal deberá realizarse básicamente con la batería estándar y los productos propios

INTRODUCTION AND OBJECTIVES: Reports show that between 25% and 78% of patients with anogenital dermatitis have positive patch test results. Consequently, patch testing would appear to be warranted in patients presenting with eczema in the anogenital region. The objectives of the present study were to identify the most common allergens in patients with perianal eczema and to determine which allergen series are most useful for patch testing in patients with this condition. MATERIAL AND METHODS: We performed a retrospective review of patch test results in patients with only perianal eczema between 2001 and 2012. RESULTS: Of the 37 patients with perianal eczema, 16 had a positive reaction; methylchloroisothiazolinone/methylisothiazolinone was the main allergen involved. With the exception of 1 case of sensitization to gentamicin, all the positive results with present relevance were to allergens from the standard series of the Spanish Contact Dermatitis and Skin Allergy Research Group (GEIDAC) or to the patient's own products. CONCLUSIONS: In our experience, methylchloroisothiazolinone/methylisothiazolinone is the main allergen involved in perianal eczema, and sensitization often results from using wet wipes. Patch testing in perianal eczema should be based on the GEIDAC standard series and the patient's own products

Practical guidelines for diagnosing hypersensitivity reactions to nonsteroidal anti-inflammatory Drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the drugs most frequently involved in hypersensitivity reactions. These reactions include various clinical entities with different mechanisms leading to the release of inflammatory mediators. Characterization of patients based on clinical manifestations and suspected underlying mechanisms is critical for implementation of adequate diagnostic procedures and patient management. Our objectives were to prepare a systematic review of available scientific evidence and to provide general guidelines for the diagnosis and management of patients with hypersensitivity reactions to NSAIDs. We also propose a practical algorithm for the diagnosis of specific types of hypersensitivity to NSAIDs and provide recommendations for the management of hypersensitive patients (AU)

Los antiinflamatorios no esteroideos (AINE) es el grupo farmacológico que más frecuentemente ha sido relacionado con las reacciones de hipersensibilidad. Estos cuadros incluyen entidades clínicas muy variadas, producidas por diferentes mecanismos, tanto inmunológicos como no inmunológicos. La caracterización de los pacientes que presentan estas reacciones se fundamenta, en las manifestaciones clínicas y la sospecha del mecanismo subyacente que la ha producido, lo que conduce a la puesta en práctica del procedimiento diagnóstico adecuado y la posterior orientación del paciente. El objetivo de este trabajo es elaborar una revisión sistemática, con las pruebas científicas disponibles, facilitando las directrices generales de diagnóstico y en consecuencia la actitud a tomar en este tipo de pacientes. Se propone un algoritmo práctico de diagnóstico para cada tipo específico de hipersensibilidad a AINE, así como proporcionar las recomendaciones a seguir en el manejo de los pacientes sensibilizados (AU)

Grado de conocimiento de las propias sensibilizaciones alérgicas en pacientes asmáticos y su repercusión en el nivel de control del asma / Knowledge of Their Own Allergic Sensitizations in Asthmatic Patients and Its Impact on the Level of Asthma Control

Introducción: Las guías clínicas de asma recomiendan la adopción de conductas de evitación alergénica. Para poder adoptarlas, los pacientes deben conocer las alergias que tienen. Sin embargo, este grado de conocimiento no ha sido hasta ahora evaluado. Los objetivos principales del estudio fueron determinar, en pacientes con asma alérgica: a) el grado de conocimiento de sus propias sensibilizaciones alérgicas; b) el porcentaje que conocen todas sus alergias y que, además, siguen normas de evitación alergénica (NEA) frente a todas ellas, y c) el eventual impacto de dicho grado de conocimiento sobre el nivel de control del asma. Pacientes y métodos: Estudio descriptivo, prospectivo y multicéntrico, con inclusión de 147 pacientes reclutados en 9 consultas externas de neumología. Tras verificar el diagnóstico previo de asma alérgica, se cumplimentó un cuestionario registrando los niveles de control y gravedad del asma, los resultados de los estudios de alergia previos, y la descripción y el número de sensibilizaciones alérgicas conocidas por el paciente y de NEA seguidas. Resultados: Tan solo 72 (49%) pacientes conocían todas sus sensibilizaciones alérgicas y únicamente 48 (33%) seguían, además, NEA frente a todos los alérgenos a los que eran alérgicos. No se demostró que existiera ninguna relación entre el grado de conocimiento de las propias sensibilizaciones alérgicas y el nivel de control del asma (p = 0,544). Conclusiones: El conocimiento global acerca de la naturaleza alérgica de su enfermedad, entre los pacientes asmáticos visitados en los servicios de neumología españoles, es insuficiente. Además, un adecuado conocimiento de las propias alergias no parece repercutir, por sí solo, en un mejor control del asma. Todo ello parece cuestionar la eficacia de las estrategias educativas actuales en este campo y, en consecuencia, estas deberían revisarse (AU)

Background: Asthma guidelines recommend the adoption of allergen avoidance measures (AAM). To do so, patients need to know their own allergies. However, this degree of knowledge has not yet been assessed. The aims of this study were to determine, in allergic asthma patients: (I) the degree of knowledge of their own allergic sensitizations; (II) the percentage of those who knew all their allergies and, in addition, adopted AAM against all of them, and (III) the possible impact of this degree of knowledge on the level of asthma control. Patients and methods: Descriptive, prospective and multicentre study, including 147 patients from 9 Respiratory Medicine outpatient clinics. After confirming the previous allergic asthma diagnosis, a questionnaire was completed. It included asthma control and severity levels, results of previous allergy tests, and the description and number of allergic sensitizations known by the patients and AAM followed. Results: Only 72 (49%) patients knew all their allergic sensitizations and only 48 (33%) were also following AAM against all the allergens to which they were allergic. No relationship was established between the degree of knowledge of their own allergies and the level of asthma control (P=0.544). Conclusions: Overall knowledge about the allergic nature of their disease among asthmatic patients attending Spanish Respiratory Medicine Departments is inadequate. Furthermore, a higher degree of knowledge of their allergies does not seem to lead, by itself, to better asthma control. Both findings seem to question the effectiveness of current educational strategies in this field and consequently, and they should be revised (AU)

Investigation of the cutaneous response to recall antigen in humans in vivo.

In this paper we provide a detailed description of an experimental method for investigating the induction and resolution of recall immune response to antigen in humans in vivo. This involves the injection of tuberculin purified protein derivative (PPD) into the skin, followed by inducing suction blisters at the site of injection, from which leucocytes and cytokines that are involved in the response can be isolated and characterized. Using this technique we found that although the majority of CD4(+) T cells in the skin that are present early in the response express cutaneous lymphocyte antigen (CLA), the expression of this marker is reduced significantly in later phases. This may enable these cells to leave the skin during immune resolution. Furthermore, interleukin (IL)-2 production can be detected both in CD4(+) T cells and also in the blister fluid at the peak of the response at day 7, indicating that mediators found in the blister fluid are representative of the cytokine microenvironment in vivo. Finally, we found that older humans have defective ability to respond to cutaneous PPD challenge, but this does not reflect a global immune deficit as they have similar numbers of circulating functional PPD-specific CD4(+) T cells as young subjects. The use of the blister technology enables further characterization of the skin specific defect in older humans and also general mechanisms that govern immune regulation in vivo.

The impact of penicillin skin testing on clinical practice and antimicrobial stewardship.

BACKGROUND: Penicillin skin testing (PST) is a simple and reliable way of diagnosing penicillin allergy. After being off the market for 4 years, penicilloyl-polylysine was reintroduced in 2009 as PRE-PEN. We describe the negative predictive value (NPV) of PST and the impact on antibiotic selection in a sample of hospitalized patients with a reported history of penicillin allergy. METHODS: We introduced a quality improvement process at our 861-bed tertiary care hospital that used PST to guide antibiotic usage in patients with a history consistent with an immunoglobulin E (IgE)-mediated reaction to penicillin. Subjects with a negative PST were then transitioned to a ß-lactam agent for the remainder of their therapy. NPV of skin testing was established at 24-hour follow-up. We are reporting the result of 146 patients tested between March 2012 and July 2012. RESULTS: A total of 146 patients with a history of penicillin allergy and negative PST were treated with ß-lactam antibiotics. Of these, only 1 subject experienced an allergic reaction to the PST. The remaining 145 patients tolerated a full course of ß-lactam therapy without an allergic response, giving the PST a 100% NPV. We estimated that PST-guided antibiotic alteration for these patients resulted in an estimated annual savings of $82,000. CONCLUSION: Patients with a history of penicillin allergy who have a negative PST result are at a low risk of developing an immediate-type hypersensitivity reaction to ß-lactam antibiotics. The increased use of PST may help improve antibiotic stewardship in the hospital setting.