Associations between pollen and allergic rhinitis in children and adolescents

Allergic rhinitis (AR) is a type of rhinitis accompanied by sensitization to allergens. One of the most clinically important allergens is pollen. Recently, due to climate change and CO 2 air pollution, the flowering period starts earlier and persists longer. In addition, antigenicity due to environmental pollution is also being strengthened. As a result, the sensitization rate to pollen antigens is on the rise. It is known that the prevalence of AR especially caused by pollen is rapidly escalating. Although the causal relationship between pollen exposure and the severity of rhinitis is not precisely established, an association of rhinitis symptoms with the time of pollen scattering exists. In addition, the mixed effect of environmental pollution and pollen may play a role in the development of rhinitis symptoms. Therefore, in order to avoid pollen, it is necessary to constantly improve pollen forecast and minimize the contact with pollen indoors and outdoors. Treatment of AR should be performed according to guidelines. Also, continuous efforts to solve the environmental problems affecting the ecology of pollen are needed.

Effects of outdoor air pollution on children with allergic rhinitis

The global worsening of air pollution has decreased the quality of life. Air pollutants can induce oxidative stress, epigenetic changes, and alterations to microRNA expression in the airway and skin, leading to immune dysregulation. Previous epidemiological studies suggest a strong association between outdoor environmental pollution and childhood allergic disease, especially allergic rhinitis (AR). Moreover, traffic-related air pollution has increased the severity and incidence of AR, and heavy traffic has been associated with an increased prevalence of AR. Thus, this review aimed to define outdoor environmental pollution and clarify the mechanisms by which air pollutants aggravate AR. In addition, we performed a systematic review and meta-analysis to summarize the findings of several domestic and international epidemiological and clinical studies about the effects of air pollution on AR in children.

Personal Exposure to Total VOC Is Associated With Symptoms of Atopic Dermatitis in Schoolchildren

Background@#The urinary levels of volatile organic compound (VOC) metabolites provide individual exposure levels compared to data obtained by measuring these compounds in ambient air. We aimed to investigate the association between personal urinary concentrations of VOC metabolites and symptoms of atopic dermatitis in schoolchildren. @*Methods@#Nine urinary VOC metabolites were analyzed from urine samples of 149 children. Diagnosis of atopic dermatitis was determined using standardized questionnaires. Pediatricians visited the schools and rated the severity of symptoms using the SCORing Atopic Dermatitis (SCORAD) in all children. @*Results@#Forty-five children (30.2%) had atopic dermatitis based on the International Study of Asthma and Allergies in Childhood (ISAAC) results and 35 children (23.8%) had symptoms of atopic dermatitis with positive SCORAD index values (defined as SCORAD ≥ 5). Children with benzylmercapturic acid detected in personal urines were associated with presence of atopic dermatitis and positive SCORAD index values. Children in the highest quartile of mandelic acid concentration were associated with presence of atopic dermatitis and positive SCORAD results. @*Conclusion@#Personal exposure to VOCs, as indicated by urinary levels of VOC metabolites, was associated with presence of atopic dermatitis and the SCORAD index value.

Risk factors and protective factors in pediatric patients with allergic rhinitis

Among allergic diseases of the Korean pediatric population, allergic rhinitis shows the most rapidly increasing prevalence. Its economic burden is substantial in many Asian countries including South Korea. This investigation of its risk factors aims to reduce the socioeconomic burden by blocking exposure of susceptible individuals to identified causes. However, the risk factors of allergic rhinitis varied considerably depending on the seasons, geographical locations, and populations involved. This review article primarily deals with studies on the risk factors for allergic rhinitis in Korean children that were published during the last 10 years and additionally investigates associated large scale international studies. Our investigation identified several single-nucleotide polymorphisms, inhalant allergens, pollution, tobacco smoke, chemicals, and family affluence as risk factors for allergic rhinitis. In contrast, breastfeeding, older sibling, and microbial diversity were protective factors against allergic rhinitis. This suggests that various genetic and environmental factors might affect the manifestation and presentation of allergic rhinitis complexly. These findings are beneficial as they can provide insights into modifiable risk factors that may hinder the development of allergic rhinitis.

Main epidemiological characteristics and natural history of pediatric allergic rhinitis

Allergic rhinitis (AR) is one of the most common allergic diseases characterized by stuffy nose, rhinorrhea, sneezing, and itching. Researchers have indicated an increase in the prevalence of AR and younger-age onset during the last few decades. The increasing burden of AR has caused many researchers to investigate time trends of the prevalence of AR and to identify its risk factors. The most commonly used epidemiological studies are cross-sectional ones such as the International Study of Asthma and Allergies in Childhood study and big data from National Health Insurance Service or National Health and Nutrition Examination Survey. However, these studies have many limitations including recall bias, selection bias, and deficit of objective evaluation. Furthermore, crosssectional studies cannot reflect new risk factors associated with the development of AR. New epidemiological studies will be needed to cover genetic factors, environmental changes, microbiomes, and lifestyles that are known to be risk factors for AR. Further studies will be needed to determine the prevalence, natural history, and risk factors of AR in order to advance our understanding of the pathophysiology, prevention, and management of comorbidities of AR.

Activated Leukocyte Cell Adhesion Molecule Modulates Th2 Immune Response in Atopic Dermatitis

PURPOSE: Activated leukocyte cell adhesion molecule (ALCAM), a member of the immunoglobulin superfamily, is highly expressed on dendritic cells. ALCAM and its receptor CD6 are co-stimulatory molecules in the immunological synapse; their interaction is required for T cell activation. While atopic dermatitis (AD) is recognized as a T helper 2 (Th2)-mediated allergic disease, the role of ALCAM in its pathogenesis is unclear. METHODS: ALCAM levels were measured in the serum of AD patients and AD-induced murine model by ovalbumin treatment. We next investigated transepidermal water loss, clinical score, Th2-immune responses, skin barrier gene expression and T-cell activation using wild-type (WT) and ALCAM deficiency mice. An oxazolone-induced AD-like model was also established and analyzed using WT- and ALCAM-deficient mice. RESULTS: We found that serum ALCAM levels were elevated in pediatric AD patients as well as WT AD mice, whereas Th2-type cytokine production and AD symptoms were suppressed in ALCAM-deficient mice. In addition, CD4+ effector T-cell counts in murine skin and skin-draining lymph nodes were lower in ALCAM-deficient mice than in their WT counterparts. ALCAM deficiency was also linked to higher expression of skin barrier genes and number of lamellar bodies. CONCLUSIONS: These findings indicate that ALCAM may contribute to AD pathogenesis by meditating a Th2-dominant immune response and disrupting the barrier function of the skin.

Association of Sensitization to Different Aeroallergens With Airway Function and Nasal Patency in Urban Children

PURPOSE: Children with sensitization to aeroallergens have decreased lung function and nasal patency. Our purpose was to determine the association of sensitization to different aeroallergens with airway function and nasal patency. METHODS: Four hundred and eighty-six randomly selected 11 year-old children who lived in Seongnam City were examined. Serum specific immunoglobulin E (IgE) levels against 6 common allergens (Dermatophagoidesfarinae, birch, cat, dog, Japanese hop and Alternaria), impulse oscillometry (IOS) results for the evaluation of airway dysfunction, and acoustic rhinometry for the determination of nasal airway patency were obtained. RESULTS: IOS indicated that children sensitized to Alternaria (n = 38, 7.8%) and dog dander (n = 69, 14.2%) had decreased lung function, based on resistance at 10 Hz (Rrs10; aβ = 0.0072; 95% CI, 0.017, 0.127; P = 0.010) and 1 Hz (Rrs1; aβ = 0.038; 95% CI, 0.001, 0.074; P = 0.042). Children sensitized to D. farinae (n = 281, 57.8%) had decreased post-decongestant nasal volume at 0 to 5 cm (aβ = −0.605; 95% CI, −1.005, −0.205; P = 0.003), but normal IOS results at all measured frequencies (P > 0.05). Increased serum eosinophil level was associated with Rrs1 (P = 0.007) and Rrs2 (P = 0.018) and post-decongestant nasal volume at 0 to 5 cm (aβ = −0.885; 95% CI, −1.331, −0.439; P < 0.001). CONCLUSIONS: Sensitivity to specific aeroallergens, serum eosinophil count and total IgE level had different associations with upper and lower airway dysfunction in urban children.

German Cockroach Extract Induces Matrix Metalloproteinase-1 Expression, Leading to Tight Junction Disruption in Human Airway Epithelial Cells

PURPOSE: Cockroach exposure is a pivotal cause of asthma. Tight junctions are intercellular structures required for maintenance of the barrier function of the airway epithelium, which is impaired in this disease. Matrix metalloproteinases (MMPs) digest extracellular matrix components and are involved in asthma pathogenesis: MMP1 is a collagenase with a direct influence on airway obstruction in asthmatics. This study aimed to investigate the mechanism by which German cockroach extract (GCE) induces MMP1 expression and whether MMP1 release alters cellular tight junctions in human airway epithelial cells (NCI-H292). MATERIALS AND METHODS: mRNA and protein levels were determined using real-time PCR and ELISA. Tight junction proteins were detected using immunofluorescence staining. Epithelial barrier function was measured by transepithelial electrical resistance (TEER). The binding of a transcription factor to DNA molecules was determined by electrophoretic mobility shift assay, while the levels of tight junction proteins and phosphorylation were determined using Western blotting. RESULTS: GCE was shown to increase MMP1 expression, TEER, and tight junction degradation. Both an inhibitor and small interfering RNA (siRNA) of MMP1 significantly decreased GCE-induced tight junction disruption. Furthermore, transient transfection with ETS1 and SP1 siRNA, and anti-TLR2 antibody pretreatment prevented MMP1 expression and tight junction degradation. An extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) inhibitor also blocked MMP1 release, ETS1/SP1 DNA binding, and tight junction alteration. CONCLUSION: GCE treatment increases MMP1 expression, leading to tight junction disruption, which is transcriptionally regulated and influenced by the ERK/MAPK pathway in airway epithelial cells. These findings may contribute to developing novel therapeutic strategies for airway diseases.

Serum Periostin Is Negatively Correlated With Exposure to Formaldehyde and Volatile Organic Compounds in Children

Epidemiological studies have shown that exposure to tobacco smoke causing irritation and inflammation in the airways tends to reduce serum periostin concentrations in adults. We now investigate prospective cross-sectional study on 135 Korean students aged 7 years in the first grade who were participating in the Seongnam Atopy Project for Children's Happiness 2016 (SAP2016) cohort. To the best of our knowledge, this is the first study to show significant inverse correlations between serum periostin concentration and exposure to xylene and formaldehyde in children. Our findings suggested the need for caution in using the serum periostin level as a marker for allergic diseases, since exposure to volatile organic compounds and formaldehyde may confound the interpretation of these results.

Clinical characteristics and genetic variation in respiratory syncytial virus isolated from infants hospitalized due to acute bronchiolitis in Korea during winter season 2016–2017

PURPOSE: Circulating patterns of predominant respiratory syncytial virus (RSV) genotypes in the community may be helpful in understanding molecular epidemiology and predicting future outbreaks of the RSV genotype. We investigated the association of genetic variations in RSV with acute severe bronchiolitis in infants. METHODS: We reviewed medical records of infants younger than 1 year of age hospitalized due to acute bronchiolitis between November 2016 and February 2017. Subjects were classified as severe or mild based on the use of mechanical or noninvasive ventilation. The associations between severity of the disease, sex, age at admission, oxygen saturation at admission and laboratory test results were analyzed. RSV sequence analysis was performed in the severe group. RESULTS: Among 114 infants, 80 underwent respiratory viral polymerase chain reaction using nasopharyngeal swab; of these, 53 (66.3%) showed positive for RSV. Of the 53 RSV-positive samples, 9 were categorized as the severe group and 44 were categorized as the mild group. Male sex, young age, longer duration of admission, minimum SaO2 at admission and bronchiolitis severity score were significantly correlated with disease severity in the severe group than in the mild group (all variables, P < 0.001). Phylogenetic and sequence analysis in the severe group revealed 8 RSV-A, ON1 genotype and 1 RSV-B, BA4 genotype. CONCLUSION: Phylogenetic types of RSV in subjects of the severe group were RSV-A, ON1 genotype or RSV-B, BA4 genotype which were prevalent in the Korean community at the same time. Our study showed that disease severity was not significantly associated with RSV genotypic evolution or antigenic drift in Korea during winter season 2016–17.

Comorbidities and Phenotypes of Rhinitis in Korean Children and Adolescents: A Cross-sectional, Multicenter Study

PURPOSE: Rhinitis is a nasal inflammatory disease in children and adolescents. However, little is known about the phenotypes and characteristics of allergic rhinitis (AR) in Korean children and adolescents. The objective of this study was to analyze the symptoms and comorbidities of rhinitis, to compare AR to non-allergic rhinitis (NAR), and to reveal the phenotypes and features of AR in a Korean pediatric population. METHODS: Patients under 18 years of age with rhinitis symptoms were recruited from January 2013 to January 2015 by pediatric allergists. We analyzed symptoms, phenotypes, comorbidities, and allergen sensitization in this cross-sectional, multicenter study. RESULTS: Medical records were collected from 11 hospitals. The AR group has 641 (68.3%) patients, with 63.2% of boys and 7.5 (±3.4) years of mean age. The NAR group has 136 (14.5%) patients, with 55.1% of boys and 5.5 (±2.9) years of mean age. Moderate-severe persistent AR affected 41.2% of AR patients. Nasal obstruction was more common in NAR patients (P<0.050), whereas AR patients sneezed more (P<0.050) and more commonly had conjunctivitis, asthma, and otitis media (P<0.050). Sinusitis was the most common comorbidity in both groups. Allergen sensitization was caused by house dust mites (HDMs) (90.2%), pollen (38.7%), and animal dander (24.8%) in AR patients. Pollen and animal dander sensitization significantly increased age-dependently (P<0.050), but 91.9% of AR patients were already sensitized to HDMs before 5 years old. CONCLUSIONS: Our study revealed that AR was more prevalent than NAR and that 41.2% of AR presented with moderate-severe disease in Korean pediatric populations. Sinusitis was the most common comorbidity, and sleep disturbance was associated with the severity of rhinitis. The majority of AR patients were sensitized to HDMs in preschool ages. Further studies, including nationwide and longitudinal data, will help understand the relationship between these diseases.

Crinical diagnostic guidelines for allergic rhinitis: medical treatment

The social and economic burden of allergic rhinitis (AR) is increasing, with significant effects on the quality of life of patients suffering from AR. Therefore, physicians require evidence-based guidelines regarding the diagnosis, differential diagnosis and proper management management of patients with AR. The Korean Academy of Asthma, Allergy and Clinical Immunology developed new clinical guidelines for the appropriate management of AR, especially in Korean patients. For the core questions (i.e. questions that most practitioners were curious about), several experts in the field of allergology, pediatrics, and otorhinolaryngology developed a set of practical guidelines based on a systematic review of the literature. Furthermore, we determined the level of evidence associated with the recommendations for each answer. In this article, we suggest 15 answers for core questions about the medical treatment of AR.

Upper airway and obstructive sleep apnea in children

Obstructive sleep apnea (OSA) is characterized by a disorder of breathing with prolonged partial and/or complete airway obstruction which causes frequent arousal during sleep. The prevalence of OSAS is approximately 2%–3.5% in children. It is mainly caused by enlarged tonsils and adenoids. Obesity, craniofacial abnormality, and neuromuscular disease are also relevant predisposing factors. Snoring is the most common presenting complaint in children with OSA, but the clinical presentation varies according to age. The pathogenesis of OSA is complex and involved in multifactorial, relative roles of anatomic and neurohumoral factors. The role of the nose is considered a component of the pathophysiology of OSA. It is unlikely that the first manifestation of OSA is intermittent snoring with nasal obstruction, often considered a coincidental finding. Childhood OSA should be diagnosed and treated, if clinically suspected, because various symptoms, signs, and consequences can be improved with proper management. Adenotonsillectomy is the first-line treatment modality in pediatric OSA with adenotonsillar hypertrophy. In addition, treatment of allergic rhinitis, nonallergic rhinitis, and other structural problems of the nasal cavity, if it is needed, may be included in the treatment of OSA.

A Survey of Korean Physicians’ Prescription Patterns for Allergic Rhinitis

OBJECTIVES: The aim of this study was to compare the prescription patterns according to characteristics of physicians using a survey distributed amongst physicians in Korea. METHODS: We surveyed the prescription patterns for allergic rhinitis (AR) of the members of the Korean Academy of Asthma, Allergy and Clinical Immunology (KAAACI) and the Korean Association of Otorhinolaryngologists (KAO). Questionnaire contained 4 categories with 28 queries. 448 physicians including 98 internal medicine (IM), 113 pediatrics (PED), and 237 otorhinolaryngology (ENT) were responded. RESULTS: Although the Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines are most frequently used in all specialties, seasonal or perennial AR is the most frequent classification system. For the definitive diagnosis of AR, ENT physicians reported using multiple allergen simultaneous test (MAST)/radio allergy sorbent test (RAST) more than others (IM, 10.9%; PED, 20.6%; ENT, 44.2%; P < 0.001). In treatment, most physicians reported that antihistamine medication is the initial treatment for AR. PED physicians prescribed fewer intranasal steroid to combinations with an antihistamine than other specialists (IM, 65.3%; PED, 42.5%; ENT, 63.3%), but preferred leukotriene antagonists (IM, 4.1%; PED, 23.0%; ENT, 3.9%; P=0.041). Overall, 53% (235/448) of the physicians performed allergen immunotherapy (AIT), and IM administers the most AIT (IM, 71.6%; PED, 42.0%; ENT, 39.5%; P=0.019). Furthermore, university and general hospital physicians prescribed more AIT than doctors at other hospital types (university hospital, 76.4%; general hospital, 64.3%; local hospital, 21.4%; private clinic, 20.2%; P < 0.001). CONCLUSION: The prescription patterns for AR were different according to the physicians’ characteristics and general rate of prescribing AIT is just about 53% in Korea. Thus, the development of complementary Korean-specific guidelines is needed and proper clinical instruction of AIT would be necessary.

Clinical diagnostic guidelines of allergic rhinitis: comprehensive treatment and consideration of special circumstances

In order to prevent sensitization to a new allergen and the development of asthma, practitioners may consider allergen-specific immunotherapy in patients with allergic rhinitis. Additionally, in patients with severe allergic rhinitis refractory to medication, practitioners can also consider surgical management for improving the patients' nasal symptoms. However, there are still no practical guidelines regarding the indications for immunotherapy, the appropriate selection of the allergen, and the optimal duration of therapy. Moreover, no clear indications exist for surgical treatment. Pregnant or lactating women frequently complain of symptoms of rhinitis. However, due to the fear of potential complications to their babies, they avoid medical treatment despite significant discomfort. Therefore, we present 14 answers to core questions about immunotherapy, surgical treatment, and considerations for special circumstances, such as pregnancy and lactation.

Prevalence of respiratory virus infection with regard to age, sex, and seasonality factors: A single center experience against children hospitalized during the 10 years

PURPOSE: It is well known that respiratory viral infection has epidemiological characteristics, including season. This study aimed to investigate the patterns of the prevalence of common respiratory viruses during a period of 10 years with regard to age, sex, and season in Korean children. METHODS: From June 2006 to November 2016, we obtained 11,798 specimens from patients aged less than 18 years who were admitted with lower respiratory infections. Ten respiratory viruses were detected using multiplex reverse transcription-polymerase chain reaction. RESULTS: Of 11,798 specimens, at least 1 virus was detected in 4,845 (41.1%). Respiratory syncytial virus (RSV, 18.9%) was the most common virus detected, followed by human rhinovirus (HRV, 14.8%), adenovirus (9.5%), and human bocavirus (HBoV, 7.4%). The detection rate of HRV was higher in male subjects (male 60.0% vs. female 40.0%, P=0.004), but the other viruses had no significant differences with regard to sex. The subjects who were positive for RSV test were youngest (median, 10.5 months; interquartile range, 3.0–25.0 months), followed by human coronavirus (median, 13.0 months), HRV (median, 14 months), and parainfluenza (median, 14 months). HBoV was most commonly detected in spring (29.3%), enterovirus in summer (25.8%), HRV in fall (22.6%), and RSV in October and winter (22.6%). CONCLUSION: We found that the prevalence of respiratory viruses in Korean children during a period of 10 years was associated with age, sex, and season when the infection occurred. Further nationwide data is warranted to infer clinical implication of our results.

Unmet Primary Physicians' Needs for Allergic Rhinitis Care in Korea

Allergic rhinitis (AR) is one of the most common chronic allergic respiratory diseases worldwide. Various practical guidelines for AR have been developed and updated to improve the care of AR patients; however, up to 40% patients remain symptomatic. The unmet need for AR care is one of the greatest public health problems in the world. The gaps between guideline and real-world practice, and differences according to the region, culture, and medical environments may be the causes of unmet needs for AR care. Because there is no evidence-based AR practical guideline reflecting the Korean particularity, various needs are increasing. The purpose of the study was to evaluate whether existing guidelines are sufficient for AR patient management in real practice and whether development of regional guidelines to reflect regional differences is needed in Korea. A total of 99 primary physicians comprising internists, pediatricians, and otolaryngologists (n=33 for each) were surveyed by a questionnaire relating to unmet needs for AR care between June 2 and June 16 of 2014. Among 39 question items, participants strongly agreed on 15 items that existing guidelines were highly insufficient and needed new guidelines. However, there was some disagreement according to specialties for another 24 items. In conclusion, the survey results demonstrated that many physicians did not agree with the current AR guideline, and a new guideline reflecting Korean particularity was needed.

Allergen sensitization and clinical characteristics in young children with atopic dermatitis

PURPOSE: Few studies have demonstrated the effects of aeroallergen sensitization on the development of atopic dermatitis (AD) in young children. This study aimed to investigate the sensitization rate of food and aeroallergens in AD patients under 2 years of age and to compare clinical characteristics between IgE- and non-IgE-mediated AD patients. METHODS: Children aged less than 2 years who had visited CHA Bundang Medical Center from 2013 through 2016 were enrolled. Allergen sensitization was measured by specific IgE levels for common allergens. Detailed information was obtained using an atopy questionnaire. RESULTS: A total of 173 patients were examined, 118 (68.2%) were male patients. The prevalence of aeroallergen sensitization under 1 year of age was 4.8% and increased to 19.5% for children aged 2 years (P=0.005). The mean age (13.6±6.3 months vs. 9.0±5.1 months, P=0.003) and the proportion of children born prematurel (15.4% vs. 2.3%, P=0.013) were higher in the aeroallergen-sensitized group than in nonsensitized group. Sensitization to food allergens between children aged less than 1 year and 2 years appeared to be similar (61.1% vs. 57.1%, P=0.651). There were no significant differences in clinical characteristics between food allergen IgE-mediated and non-IgE-mediated AD children. CONCLUSION: Aeroallergen sensitization increased markedly in AD patients aged 2 years which is about 4 times that of the general population. However, there were no significant differences in clinical manifestations between allergen IgE-mediated and non-IgE-mediated AD children in both food and aeroallergens.

Prevalence and Risk Factors of Urticaria With a Focus on Chronic Urticaria in Children

PURPOSE: Limited data is available on the prevalence and risk factors of acute and chronic urticaria in children. Our purpose was to determine the prevalence and identify the risk factors of acute and chronic urticaria in Korean children. METHODS: This population-based study examined 4,076 children (age 4 to 13 years) who were enrolled in the 2015 prospective Seongnam Atopy Project (SAP 2015) in Korea. The parents completed an urticaria questionnaire that included questions regarding the duration, severity, and triggering factors of urticaria. Blood sampling (n=464) was performed to measure vitamin D, total eosinophil count (TEC), and total IgE levels, and skin prick tests (n=503) were done. RESULTS: The prevalences of the life-time, acute, and chronic urticaria were 22.5%, 13.9%, and 1.8% (chronic continuous urticaria, 0.7%; and chronic recurrent urticaria, 1.1%), respectively. Acute urticaria was significantly associated with allergic diseases and parental history of allergy (P<0.001), but chronic urticaria was not associated with these clinical factors. There was no significant difference in the 25-hydroxyvitamin D level between subjects with chronic urticaria and controls (P=0.124). Chronic continuous urticaria was associated with living in a new residence (aOR=2.38, 95% CI=1.02-5.54, P=0.044) and belonging to a family with a high income (aOR=4.24, 95% CI=1.24-14.56, P=0.022). CONCLUSIONS: A total of 1.8% of children were found to have chronic urticaria. Living in a new residence and belonging to a family with a high income increased the risk of chronic continuous urticaria.

Clinical diagnostic guidelines for allergic rhinitis: diagnosis

As the prevalence and socioeconomic burden of allergic rhinitis is steadily increasing every year, it is essential that clinical practitioners diagnose and manage allergic rhinitis in an evidence-based manner. Therefore, the Korean Academy of Asthma, Allergy and Clinical Immunology developed new clinical guidelines for Korean patients and practitioners. We first performed a questionnaire survey to address the core questions, about which clinical practitioners are the most curious. A large group of physicians (allergists), pediatricians, and otorhinolaryngologists developed answers for those questions by performing a systematic literature review and determining the appropriate levels of recommendation. In this article, we propose 11 answers for core questions regarding the diagnosis and differential diagnosis of allergic rhinitis.