The hygiene hypothesis, first proposed in 1989, suggested that reduced exposure to infections in early life leads to allergic diseases by the defects in the establishment of immune tolerance. Although many studies provided evidence that some exposure conditions, including family size, antibiotics, probiotics, and viral or bacterial infections, are strongly related to the prevalence of allergic diseases, thereby supporting the hygiene hypothesis, some evidence does not provide acceptable results for the hygiene hypothesis. Further, most studies have focused on patients with asthma or atopic dermatitis, not allergic rhinitis. In this review, we summarize the recent studies for and against the ‘hygiene hypothesis’ and identify causal association with the prevalence of allergic rhinitis.

Primary pneumatization of the frontal bone occurs in the first year of life, but further pneumatization continues until 18 years of age. Elongation of the ethmoidal infundibulum and frontal recess, or upwards migration of the anterior ethmoidal cells has been proposed as a mechanism of frontal sinus development. The frontal sinus drainage pathway is displaced in the anterior or posterior direction depending on the pneumatization pattern of the frontoethmoidal cells. Also, frontal sinuses can be connected to the infundibulum or directly to the middle meatus depending on the superior attachment pattern of the uncinate process. Bilateral frontal sinuses are separated by their bony septum, and thus have their own drainage pathways. Contrary to this general rule, we experienced two cases of frontal sinuses that were connected to each other, showing a single drainage pathway from both frontal sinuses. We report these two cases along with a literature review.

Semantic variant primary progressive aphasia (svPPA), a well-known subtype of the frontotemporal dementia often shows peculiar clinical features and structural neuroimage findings. To strengthen the accuracy of a clinical diagnosis, amyloid positron emission tomography-computed tomography (PET-CT) might be helpful. However, in patients with late-onset svPPA, an admixture of the various neuropathology would interfere with diagnostic approach. Herein, we report a case of late-onset bilateral svPPA showing a regional amyloid deposition on PET-CT scan.

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.

Cedrol, a sesquiterpene alcohol, isolated from Juniperus chinensis has been reported to inhibit minichromosome maintenance (MCM) proteins as cancer biomarkers in human lung cancer in vitro. In the present study, we investigated the anti-cancer activity of cedrol in vitro and in vivo using human colorectal cancer HT29 cells and a human colorectal tumor xenograft model. Cedrol inhibited MCM protein expression and cell growth in HT29 cells, which are associated with G1 arrest and the induction of apoptosis. We demonstrated that cedrol effectively reduced HT29 tumor growth without apparent weight loss in a human tumor xenograft model.Compared with vehicle- and adriamycin-treated tumor tissues, cedrol induced changes in the tumor tissue structure, resulting in a reduced cell density within the tumor parenchyma and reduced vascularization. Moreover, the expression of MCM7, an important subunit of MCM helicase, was significantly suppressed by cedrol in tumor tissue. Collectively, these results suggest that cedrol may act as a potential anti-cancer agent for colorectal cancer by inhibiting MCM protein expression and tumor growth.

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.

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.

The prevalence of allergic rhinitis in children and adolescents is constantly increasing. However, few studies exist on the relationship between smoking and allergic rhinitis. In addition to conventional cigarettes, electronic and heated cigarettes have recently been introduced, which have several harmful effects. It is hypothesized that smoking and rhinitis are correlated; however, this relationship is complex. Previous studies reported that exposure to smoking during pregnancy is associated with allergic rhinitis development.Unlike the varied results reported in adults, studies on children and adolescents have often correlated direct/indirect smoke with allergic rhinitis, with prolonged exposure being associated with a higher risk of allergic rhinitis, particularly when exposed at an early age. Nonallergic inflammatory reactions and immunoglobulin E-mediated allergic sensitization are assumed to be the underlying mechanisms for the association between allergic rhinitis and smoking. Measures to reduce smoking are warranted to lower the incidence of allergic rhinitis in children and adolescents and to improve their health.

The incidence of coronavirus diseases 2019 (COVID-19), including severe cases, has been increasing in both children and adolescents with the spread of the delta variant. COVID-19 vaccines have been identified to be effective in the prevention of COVID-19transmission in children and adolescents and keeping schools open. However, adverse reactions associated with COVID-19 vaccination in children and adolescents contribute to parents’ hesitation to proceed with vaccination, especially due to serious, albeit rare, reactions. The results from COVID-19 vaccine clinical trials on the safety and efficacy of COVID-19 vaccines in children and adolescents are promising in terms of their effects on COVID-19 infection prevention. In the present study, we summarize the adverse reactions of COVID-19 vaccines in children and adolescents, based on the clinical trials, mainly including Pfizer-BioNTech and Moderna COVID-19 vaccines. In the Pfizer-BioNTech COVID-19 clinical trials, the most common local adverse reaction was pain at the injection site in 74.1%–86%, depending on age, and the most common systemic adverse reaction was fatigue, followed by headache, myalgia, diarrhea, and fever with differences in the distribution according to age. There was no severe adverse reaction related to any COVID-19 vaccine in children and adolescents during the study period. In the mass vaccination program of COVID-19 in children and adolescent, myocarditis has rarely been diagnosed after COVID-19 vaccination, which most commonly occurred in boys after the second dose. Currently, Pfizer-BioNTech COVID-19 vaccines can be safely recommended in children and adolescents for the prevention of COVID-19 infection and the reduction in COVID-19 severity.