Alternaria Allergy and Immunotherapy.

BACKGROUND: Allergen immunotherapy (AIT) is the only known causative treatment for Alternaria allergy, but the difficulty in standardizing Alternaria extracts hampers its effectiveness and safety. SUMMARY: Alternaria, a potent airborne allergen, has a high sensitization rate and is known to trigger the onset and exacerbation of respiratory allergies, even inducing fungal food allergy syndrome in some cases. It can trigger a type 2 inflammatory response, leading to an increase in the secretion of type 2 inflammatory cytokines and eosinophils, which are the culprits behind allergic symptoms. Diagnosing Alternaria allergy is a multistep process, involving a careful examination of clinical symptoms, medical history, skin prick tests, serum-specific IgE detection, or provocation tests. Alt a1, the major component of Alternaria, is a vital player in diagnosing Alternaria allergy through component-resolved diagnosis. Interestingly, Alternaria can reduce the protein activity of other allergens like pollen and cat dander when mixed with them. In order to solve the problems of standardization, efficacy and safety of traditional Alternaria AIT, novel AIT methods targeting Alt a1 and innovative vaccines such as epitope, DNA, and mRNA vaccines seem promising in bypassing the standardization issue of Alternaria extracts. But these studies are in early stages, and most researches are still focused on animal models, calling for more evidence to validate their use in humans. KEY MESSAGES: This review delves into the various aspects of Alternaria allergy, including characteristics, epidemiology, immune mechanisms, diagnosis, clinical manifestations, and the application and limitations of Alternaria AIT, aiming to provide a foundation for the management of patients with Alternaria allergy.

Allergen Component Testing: Key in Diagnosing Atypical Pollen-Food Allergy Syndrome.

This case report details the complex presentation, diagnosis, and management of a teenager with pollen-food allergen syndrome (PFAS), formerly known as oral allergy syndrome. PFAS, mediated by immunoglobulin E (IgE) antibodies, stems from the cross-reactivity between pollens and uncooked plant-based foods, leading to a spectrum of symptoms, such as itching or tingling of the oral cavity. A UK survey indicated an average PFAS prevalence of 2%, with apples, hazelnuts, and kiwifruit commonly implicated. The presented case involved a 15-year-old girl referred from the respiratory clinic to the allergy clinic due to episodes of sore throat and urticaria rash following Nutella (chocolate paste containing hazelnut) and peanut consumption. Extensive diagnostic measures, including specific IgE testing, skin prick tests, and allergen component testing, revealed cross-reactivity between Bet v 1 and hazelnut allergens. The patient's atopic history, encompassing poorly controlled asthma, allergic rhinitis, and eczema, added layers of complexity to the diagnosis. Management strategies comprised dietary advice, allergen avoidance, and potential consideration of aeroallergen immunotherapy. A comprehensive dietary plan emphasized abstaining from specific foods and raising awareness of potential reactions. The patient, following guidance from the allergy clinic, exhibited improvements in allergic rhinitis and oral symptoms. This case underscores the importance of allergen component testing in diagnosing atypical PFAS presentations and tailoring management plans. Ongoing collaboration between healthcare providers, detailed patient education, and regular follow-ups are crucial for effective PFAS management and long-term care.

[Study on allergen components of birch pollen in Beijing area].

Objective:To explore the allergen components of birch pollen in the Beijing area and interpret its clinical significance. Methods:A total of 58 patients with birch pollen allergy were included in the cross-sectional study and divided into allergic rhinitis（AR） and allergic asthma（AA） groups according to clinical manifestations. Concentration of birch pollen allergen sIgE, as well as Bet v 1, Bet v 2, Bet v 4 and Bet v 6 sIgE were detected by ImmunoCAP immunolinked immunoassay. Differences of sIgE concentration of birch pollen allergen component in AR and AA were analyzed. Results:There were 44（75.9%） cases of AR and 14（24.1%） cases of AA were enrolled. All the 18 patients with spring pollen allergy were AR patients without AA. There were 40 cases with both spring and autumn pollen allergy, of which 26 cases（65%） were AR and 14 cases（35%） were AA. The sIgE of birch pollen allergen was level 2 or above in all subjects. 94.8% were positive for any four allergen components. 77.6% were mono-sensitized to any allergen component while 17.2% were dual-sensitized. The positive rate of Bet v 1 and/or Bet v 2 was 93.1%. The positive rates of four protein components were: Bet v 1（82.8%）, Bet v 2（29.3%）, Bet v 6（1.7%）, Bet v 4（0%）. sIgE of birch pollen was positively correlated with sIgE level of Betv 1（r=0.898, P<0.001）. The sIgE concentration of Bet v2 in AA group was significantly higher than that in AR group（[4.34±14.35] kUA/L vs [1.56±3.26] kUA/L, P<0.05）. There was no significant difference in other components. Conclusion:Bet v 1 is the main allergen component of birch pollen in the Beijing area, and Bet v 1 plus Bet v 2 can diagnose more than 90% of birch pollen allergy.

[A MULTICENTER CLINICAL SURVEY ABOUT THE PREVALENCE OF JAPANESE CYPRESS POLLINOSIS AND THE EFFICACY OF SUBLINGUAL IMMUNOTHERAPY WITH JAPANESE CEDAR POLLEN EXTRACT DURING JAPANESE CYPRESS POLLEN DISPERSAL PERIOD].

BACKGROUND: Little is known whether sublingual immunotherapy using Japanese cedar pollen extract (cedar SLIT) is effective for not only Japanese cedar pollinosis but also Japanese cypress pollinosis. We investigated the prevalence rate of Japanese cypress pollinosis, efficacy of cedar SLIT on cypress pollinosis and patients' wish to receive cypress SLIT. METHODS: We investigated a multi-center (31 institutions), cross-sectional survey using a self-administrated questionnaire with four questions for patients received cedar SLIT aged from 5 to 69 years old. RESULTS: 2523 subjects were enrolled for analysis. 83.4% of them had pollinosis symptoms during cypress season before cedar SLIT. In such patients, 37.4% experienced lessened efficacy of cedar SLIT during cypress season. Both the prevalence of cypress pollinosis and the lessened efficacy of cedar SLIT on cypress pollinosis were significantly seen in western Japan as compared to eastern Japan. 76.1% of the subject having cypress pollinosis before SLIT wished to receive cypress SLIT if it is available. CONCLUSION: A lessened efficacy of cedar SLIT during cypress season was broadly seen in Japan, and further showed a regional difference. Together with the finding of high wish by patients, these results suggest a development of cypress SLIT is desirable.

Profiles of Birch Allergen Component Sensitization and Its Association with Pollen Food Allergy Syndrome in Northern China.

Purpose: To investigate the major allergen components associated with birch pollen allergy in northern China and elucidate clinical relevance to pollen food allergy syndrome (PFAS). Methods: Fifty-eight patients were recruited for a cross-sectional study and categorized into two groups: PFAS group and non-PFAS group, as well as apple allergy group and non-apple allergy group. The sIgE levels of birch pollen and its components, namely Bet v 1, Bet v 2, Bet v 4, and Bet v 6, were analyzed. Results: Among 58 participants, 44 individuals (75.9%) reported PFAS. 32 out of 44 (72.7%) participants reported apple allergy. Bet v 1 exhibited the highest sensitization rate at 82.8%, followed by Bet v 2 (29.3%) and Bet v 6 (1.7%). The combined sensitization rate for Bet v 1 and/or Bet v 2 was 93.1%. A total of 77.6% of the subjects demonstrated sensitization to single component, while 19.0% exhibited sensitization to two components. The sIgE levels of birch pollen and Bet v 1 were significantly elevated in PFAS group compared to non-PFAS group (p=0.001, p<0.001, respectively), as well as in apple-allergic and non-apple-allergic group (p<0.001, p<0.001, respectively). The optimal cut-off values for birch pollen and Bet v 1 sIgE were determined to be 7.09 kUA/L (with a sensitivity of 84.1% and specificity of 78.6%) and 5.11 kUA/L (with a sensitivity of 75.0% and specificity of 85.7%) when diagnosing PFAS. In terms of apple allergy, the optimal cut-off value were 9.40 kUA/L (with a sensitivity of 81.3% and specificity of 76.9%) and 6.53 kUA/L (with a sensitivity of 84.4% and specificity of 84.6%), respectively. Conclusion: The predominant sensitization pattern is mono-sensitization to Bet v 1, but when considering immunotherapy, Bet v 2 should also be taken into account. Bet v 1 serves as a valuable biomarker for diagnosing PFAS and apple allergy.

Early inhalant allergen sensitization at component level: an analysis in atopic Dutch children.

Background: Allergic rhinitis is a common respiratory disease in children and sensitization to inhalant allergens plays a significant role in its development. However, limited knowledge exists regarding sensitization profiles of inhalant allergen components in atopic children, particularly in the very young individuals. Understanding these profiles could provide insights into the early development of allergic rhinitis. The objective of this cross-sectional retrospective study was to evaluate the IgE-sensitization profiles to multiple inhalant allergen components and their clinical relevance in Dutch atopic children, with specific focus on children under the age of 4 years. Methods: A total of 243 atopic children were included in the study and sensitization profiles were analyzed using multiplex microarray analysis (ISAC). Clinical information was obtained from records of a pediatric allergy outpatient clinic between 2011 and 2020. Specific IgE responses to inhalation allergen components from five allergen sources (grass pollen, tree pollen, house dust mite, cat and dog), were examined. The study encompassed children of different age groups and compared those with and without symptoms. Results: The results demonstrated that sensitization to inhalant allergen components was present in 92% of the cohort. Sensitization was already evident at a young age (87%), including infancy, with a rapid increase in prevalence after 1 year of age. House dust mite emerged as the most predominant sensitizing allergen in early childhood, followed by tree pollen in later years. Sensitization patterns were similar between symptomatic and asymptomatic children, although symptomatic children exhibited higher frequencies and values. The sensitization profiles in very young children were comparable to those of children across all age groups. Conclusion: These findings highlight the presence of sensitization to inhalant allergen components and the early onset of allergic rhinitis before the age of 4, including infancy, in Dutch atopic children. Notable allergen molecules in Dutch atopic children under the age of 4 years include Bet v 1, Fel d 1, Der f 1, Der p 1, Der p 10 and Phl p 4, with house dust mite sensitization being the most common among Dutch infants. Moreover, the prevalence of sensitization to inhalant allergens in this Dutch cohort surpassed that of general European populations, emphasizing the importance of early assessment and management of allergic rhinitis in young atopic children.

Selected Technical Aspects of Molecular Allergy Diagnostics.

Diagnosis of allergic diseases is a complex, multi-stage process. It often requires the use of various diagnostic tools. The in vitro diagnostics (IVD), which includes various laboratory tests, is one of the stages of this process. Standard laboratory tests include the measurement of the serum concentration of specific immunoglobulin E (sIgE) for selected allergens, full allergen extracts and/or single allergen components (molecules). The measurement of IgE sIgE to the allergen components is called molecular allergy diagnosis. During the standard laboratory diagnostic process, various models of immunochemical tests are used, which enable the measurement of sIgE for single allergens (one-parameter tests, singleplex) or IgE specific for many different allergens (multi-parameter tests, multiplex) in one test. Currently, there are many different test kits available, validated for IVD, which differ in the method type and allergen profile. The aim of the manuscript is to present various technical aspects related to modern allergy diagnostics, especially in the area of molecular allergy diagnostics.

Serological analysis of allergic components of house dust mite provides more insight in epidemiological characteristics and clinical symptom development in North China.

Background: House dust mite (HDM) is the most common airborne source causing complex allergy symptoms. There are geographic differences in the allergen molecule sensitization profiles. Serological testing with allergen components may provide more clues for diagnosis and clinical management. Objective: This study aims to investigate the sensitization profile of eight HDM allergen components in a large number of patients enrolled in the clinic and to analyze the relation of gender, age, and clinical symptoms in North China. Methods: The 548 serum samples of HDM-allergic patients (ImmunoCAP® d1 or d2 IgE ≥0.35) were collected in Beijing City and divided in four different age groups and three allergic symptoms. The specific IgE of HDM allergenic components, Der p 1/Der f 1, Der p 2/Der f 2, Der p 7, Der p 10, Der p 21, and Der p 23, was measured using the micro-arrayed allergen test kit developed by Hangzhou Zheda Dixun Biological Gene Engineering Co., Ltd. The new system was validated by comparing to single-component Der p 1, Der p 2, and Der p 23 tests by ImmunoCAP in 39 sera. The epidemiological study of these IgE profiles and the relation to age and clinical phenotypes were analyzed. Results: A greater proportion of male patients was in the younger age groups, while more female patients were in the adult groups. Both the sIgE levels and the positive rates (approximately 60%) against Der p 1/Der f 1 and Der p 2/Der f 2 were higher than for the Der p 7, Der p 10, and Der p 21 components (below 25%). The Der f 1 and Der p 2 positive rates were higher in 2-12-year-old children. The Der p 2 and Der f 2 IgE levels and positive rates were higher in the allergic rhinitis group. The positive rates of Der p 10 increased significantly with age. Der p 21 is relevant in allergic dermatitis symptom, while Der p 23 contributes to asthma development. Conclusion: HDM groups 1 and 2 were the major sensitizing allergens, with group 2 being the most important component relevant to respiratory symptoms in North China. The Der p 10 sensitization tends to increase with age. Der p 21 and Der p 23 might be associated with the development of allergic skin disease and asthma, respectively. Multiple allergen sensitizations increased the risk of allergic asthma.

Allergy screening with extract-based skin prick tests demonstrates higher sensitivity over in vitro molecular allergy testing.

BACKGROUND: As extract-based skin testing as well as in vitro tests for major allergens have their own advantages, both procedures are usually performed in routine settings. In times of shortages in medical staff and supplies, we asked ourselves, how many patients would be underdiagnosed, if only one test could be used. METHODS: In a retrospective analysis, we investigated a cohort of 2646 patients seen by a single physician in a large Austrian outpatient allergy clinic in 2018. Only patients with an allergen source-specific history and pairs of extract-based skin prick (SPT) and in vitro molecular allergy tests to major allergens were included. RESULTS: For all tested allergen sources, sensitivity was higher for SPT than for sIgE-based molecular allergy testing. Concerning 1006 birch pollen-allergic patients, 791 (78.6%) had positive results with both tests, while 153 (15.2%) only with the SPT and 62 (6.2%) only with the sIgE to Bet v1. The other allergen sources showed similar results: For house dust mite 816/1120 (72.9%), grass pollen 1077/1416 (76.1%) and cat 433/622 (69.6%) remained test-positive with both procedures, whereas in 276 (24.6%), 224 (15.8%) and 173 (27.8%) times only the SPT and 28 (2.5%), 115 (8.1%) and 16 (2.6%) times only the sIgE to Der p1/2/23, Phl p1/5 and Fel d1 showed a positive result. Each comparison was statistically significant (each p < 0.0001, Chi-squared test). CONCLUSIONS: Screening for allergy with major molecular allergens has lower sensitivity when compared with extract-based skin tests. A combination of both is required for an optimal sensitivity.

Component-Resolved Diagnosis Based on a Recombinant Variant of Mus m 1 Lipocalin Allergen.

Exposure to the Mus m 1 aeroallergen is a significant risk factor for laboratory animal allergy. This allergen, primarily expressed in mouse urine where it is characterized by a marked and dynamic polymorphism, is also present in epithelium and dander. Considering the relevance of sequence/structure assessment in protein antigenic reactivity, we compared the sequence of the variant Mus m 1.0102 to other members of the Mus m 1 allergen, and used Discotope 2.0 to predict conformational epitopes based on its 3D-structure. Conventional diagnosis of mouse allergy is based on serum IgE testing, using an epithelial extract as the antigen source. Given the heterogeneous and variable composition of extracts, we developed an indirect ELISA assay based on the recombinant component Mus m 1.0102. The assay performed with adequate precision and reasonable diagnostic accuracy (AUC = 0.87) compared to a routine clinical diagnostic test that exploits the native allergen. Recombinant Mus m 1.0102 turned out to be a valuable tool to study the fine epitope mapping of specific IgE reactivity to the major allergen responsible for mouse allergy. We believe that advancing in its functional characterization will lead to the standardization of murine lipocalins and to the development of allergen-specific immunotherapy.

[Profiles of IgE sensitization to dust mite allergen components in patients with allergic rhinitis and asthma].

Objective:To study the differences and clinical significance of dust mite allergen components in allergic rhinitis（AR） and allergic rhinitis with asthma syndrome（ARAS） patients. Methods:The clinical data of 42 AR patients were retrospectively analyzed and patients were divided into AR and ARAS group. The serum sIgE concentrations of house dust mites were detected by ImmunoCAP system. The allergen components of Der p（Der p 1, Der p 2, Der p 7, Der p 10, Der p 21, Der p 23） and Der f（Der f 1, Der f 2） were analyzed by protein microarray method. The concentration differences of dust mite allergen and its components in AR and ARAS groups were analyzed. Results:Thirty-one cases of AR and 11 cases of ARAS were included. The positive rate of Der p and Der f was 100.0% and 97.6%, respectively. The highest sensitization rates of Der p allergen components were as following: Der p 1（73.8%）, Der f 1（66.7%）, Der f 2（64.3%） and Der p 2（61.9%）. The sensitization rates of Der f 1（100.0% vs 54.8%, P=0.006）, Der p 2（90.9% vs 51.6%, P=0.021） and Der f 2（100.0% vs 51.6%, P=0.004） in ARAS group were significantly higher than those in AR group. The sIgE concentrations of Der p in AR group were significantly lower than those in ARAS group（[7.65±12.15]kUA/L vs[15.20±18.77]kUA/L, P<0.05）. The sIgE concentrations of Der p 1（[5.39±4.61]kUA/L vs[2.03±2.97]kUA/L, P=0.013）, Der p 2（[8.82± 13.58]kUA/L vs[2.78±5.80]kUA/L, P=0.001）, Der p 23（[1.76± 3.88]kUA/L vs[0.28±0.65]kUA/L, P<0.001） was significantly higher in ARAS group than that of AR group. Correlation analysis showed that Der p 1, Der p 2, Der f 1 and Der f 2 had high positive correlation（P<0.01）. The dust mite components sensitization showed a multiple-sensitized mode. 66.7% of the 42 patients were positive for two or more components while it was 58.1% of the AR group and 90.9% of the ARAS group. The sensitization rate of 3 or more components in ARAS group was significantly higher than that in AR group（54.6% vs 29.1%, P<0.05）. Conclusion:The concentration of dust mites allergens in ARAS group is higher than that in AR group. Der p 1, Der f 1, Der p 2 and Der f 2 are the main allergen components with a higher sensitization rate in ARAS group. The concentrations of Der p 1, Der p 2 and Der p 23 were higher in ARAS group. The ARAS group is prone to multi-sensitzed to allergen components.

Major Grass Pollen Allergen Components and Cross-Reactive Carbohydrate Determinants in Mugwort-Sensitized Child Patients With Allergic Respiratory Disease in Western China.

Mugwort is a common pollen allergen in western China, and this study aimed to investigate the patterns of molecular sensitization to major grass pollen allergens (mugwort, ragweed, bermuda grass, and timothy grass) and cross-reactive carbohydrate determinants (CCD) in children who were sensitized to mugwort in western China. Serum-specific IgE (sIgE) of major allergen components and CCD were detected among 121 mugwort SPT-positive children via the EUROBlotMaster system if the mugwort-sIgE was positive (MSP). A CCD inhibition test was further performed on the serum of patients with positive CCD-sIgE. Latent class analysis was used to identify the patterns of potential sensitization to major grass pollen allergens. Of a total of 100 patients with mugwort-sIgE positive (MSP), 52.0, 41.0, and 31.0% of them were positive to Art v 1, Art v 3, and Art v 4, respectively. An optimal model with three latent classes was determined using grass pollen allergens, components, and CCD. The sensitization patterns can be summarized as (1) MSP and cosensitized to ragweed, bermuda grass, and timothy grass (23.74%); (2) MSP and cosensitized to Art v 1 (54.08%); (3) MSP and cosensitized to Art v 4, Cyn d 12, Phl p 12 (22.18%). Additionally, CCD sIgE levels had a significant positive correlation with ragweed, bermuda grass, and timothy grass (P < 0.05), and CCD-Inhibitor can highly inhibit the above allergens sIgE. Our findings suggest that Art v 4 was the typical cross-reaction component of mugwort, which is cosensitized to Phl p 12 and Cyn d 12. A wide cross-reaction among ragweed, bermuda grass, and timothy grass caused by CCD was observed.

Association between allergen component sensitisation and clinical allergic disease in children.

BACKGROUND: Allergen component sensitisation testing is becoming increasingly important in the diagnosis of peanut allergy. The aim of the present study was to evaluate the relationship between sensitisation and symptoms of allergic disease in children by testing a large panel of inhalants, food allergens, and allergen components. METHODS: For 287 children visiting our laboratory for allergy testing, symptoms of allergic disease were recorded by standardised validated questionnaires. Specific IgE to 11 whole allergens was assessed by ImmunoCAP, and to 112 allergen components by ISAC ImmunoCAP assay. We used latent class analysis (LCA) to distinguish clinical phenotypes. RESULTS: Inhalant and food allergen sensitisation was common, irrespective of the children's allergic symptom type. Less than 10% of the variance in symptom scores was explained by variations in the number of allergens (components) that the child was sensitised to. In LCA, 135 children (50.2%) had mild allergy, with few symptoms and sensitisation to no or few allergens, 74 children (27.5%) had more symptoms and sensitisation to inhalant allergens (respiratory allergy) and 60 children (22.3%) showed polysensitisation to a median of six allergens and had more severe symptoms of different organ systems. Adding allergen component test results to LCA failed to result in identifiable classes of allergic disease in children. CONCLUSIONS: In this group of children with allergic symptoms, referred for allergy testing by their physician, broad screening for allergen component sensitisation did not contribute to distinguishing phenotypes of allergic disease.

Association between allergen component sensitisation and clinical allergic disease in children

Background Allergen component sensitisation testing is becoming increasingly important in the diagnosis of peanut allergy. The aim of the present study was to evaluate the relationship between sensitisation and symptoms of allergic disease in children by testing a large panel of inhalants, food allergens, and allergen components.Methods For 287 children visiting our laboratory for allergy testing, symptoms of allergic disease were recorded by standardised validated questionnaires. Specific IgE to 11 whole allergens was assessed by ImmunoCAP, and to 112 allergen components by ISAC ImmunoCAP assay. We used latent class analysis (LCA) to distinguish clinical phenotypes.Results Inhalant and food allergen sensitisation was common, irrespective of the children’s allergic symptom type. Less than 10% of the variance in symptom scores was explained by variations in the number of allergens (components) that the child was sensitised to. In LCA, 135 children (50.2%) had mild allergy, with few symptoms and sensitisation to no or few allergens, 74 children (27.5%) had more symptoms and sensitisation to inhalant allergens (respiratory allergy) and 60 children (22.3%) showed polysensitisation to a median of six allergens and had more severe symptoms of different organ systems. Adding allergen component test results to LCA failed to result in identifiable classes of allergic disease in children.Conclusions In this group of children with allergic symptoms, referred for allergy testing by their physician, broad screening for allergen component sensitisation did not contribute to distinguishing phenotypes of allergic disease (AU)

Correlation between sensitization to house dust mite major allergens, age, and symptoms in Japanese house dust mite allergic subjects.

Der p 23 has recently been recognized as a new house dust mite (HDM) major allergen that may be linked to the development of asthma in HDM allergic patients. This study aimed to investigate the frequency of sensitization to HDM major allergen components including Der p 23 and to examine the correlation between HDM-sensitization and AR symptom score in Japanese HDM allergic rhinitis (AR) patients without allergic asthma. Serum samples (n = 120) collected from Japanese HDM AR patients (12 to 64 years) without asthma were assessed for allergen-specific IgE (s-IgE) by ImmunoCAP (Dermatophagoides pteronyssinus (D. pteronyssinus; Der p) extract, Der p 23) or immunosolid-phase allergen chip (Der p 1, Der p 2). Japanese HDM AR patients without asthma showed a high prevalence of allergic sensitization to the HDM major allergens Der p 1 (94.2%), Der p 2 (97.5%) and Der p 23 (71.7%). No difference in the prevalence was detected for Der p 1 and Der p 2 s-IgE among three age groups. However, the prevalence of Der p 23 s-IgE was significantly higher in the younger group compared to the elderly group. No significant correlation was found between AR symptom scores and concentration of s-IgE towards Der p extract and any of the three HDM major allergens. Although the prevalence of sensitization towards D. pteronyssinus major allergens is high in Japanese AR patients without asthma, there was no correlation between allergen specific IgE including IgE towards Der p 23 and AR symptom in this population.

Molecular Allergy Diagnosis in Clinical Practice: Frequently Asked Questions.

Considerable progress has been made in the field of molecular biology in recent years, enabling the study of sensitization to the individual components of an allergenic source, a practice that has been termed molecular allergy diagnosis (MD) or component-resolved diagnosis (CRD). The present review provides the clinician with a practical approach to the use of MD by answering questions frequently asked by physicians on how MD can help improve the diagnosis of allergy in daily clinical practice. The article is divided into 3 sections. First, we provide a brief review of the importance for the clinician of knowing the main allergens in the different allergenic sources, their structure, and their in vitro cross-reactivity before approaching MD (section A). Second, we review the usefulness of MD in clinical practice (section B) and answer frequently asked questions on the subject. Finally, section C addresses the interpretation of MD and its integration with other tools available for the diagnosis of allergy.