October 2020

Allergic rhinitis and allergic sensitization are the most common and prevalent allergic conditions in the world. It has been suggested that serum 25-hydroxyvitamin D might have a role in immunomodulation and, consequently, in allergic rhinitis and allergic sensitization. This study aimed to assess a causal association between 25-hydroxyvitamin D levels and risk of allergic rhinitis or allergic sensitization, using two-sample Mendelian randomization (MR) approach.

Instrumental variables identified seven single nucleotide polymorphisms (SNPs) associated with serum 25-hydroxyvitamin D levels. The primary objective was allergic rhinitis, and the secondary objectives were allergic sensitization and non-allergic rhinitis. Two cohort studies provided the genome-wide association summary statistics of the outcomes. MR analysis with a random-effects inverse variance weighted method was performed as the primary analysis to estimate the overall effect size. Sensitivity analysis using the weighted median method and MR-Egger regression method was conducted. A subgroup analysis based on 25-hydroxyvitamin D synthesis-SNPs was also applied.

There wasn’t a causal association between serum 25-hydroxyvitamin D and risk of allergic rhinitis, and subgroup analysis also showed no relation between 25-hydroxyvitamin D synthesis-related SNPs and outcomes. The same results were obtained for sensitivity analysis.

In conclusion, this study did not find any evidence that supports a causal association between serum 25-hydroxyvitamin D levels and risk of allergic rhinitis, allergic sensitization, or non-allergic rhinitis in the European-ancestry population. This conclusion is against the use of vitamin D supplementation for the prevention of allergic diseases.

The prevalence of allergic rhinitis has been increasing, with more than one in five people being affected. The objective of this study was to evaluate the validity of 13 different Danish prescription algorithms and hospital data to identify people with allergic rhinitis.

This study included 10 653 Danish adults in two time periods. Investigators used a positive serum-specific IgE and self-reported nasal symptoms as the primary gold-standard of allergic rhinitis. The secondary gold standard of allergic rhinitis was self-reported physician diagnosis. They calculated sensitivity, specificity, positive predictive value (PPV), negative predictive value, and corresponding 95 % confidence intervals for each register-based algorithm in the two periods.

All algorithms had a low sensitivity, irrespective of the definition of allergic rhinitis or period. The highest positive predictive values were achieved for algorithms that required antihistamines and intranasal corticosteroids, with a value of 0.69 (0.62 – 0.75) and a corresponding sensitivity of 0.10 (0.09 – 0.12) for the primary gold standard of allergic rhinitis.

In conclusion, due to the low use of prescription medication among those with allergic rhinitis, sensitivity was low (≤ 0.40) for all algorithms irrespectively of the definition of allergic rhinitis. Algorithms based on antihistamines and intranasal corticosteroids granted the highest PPVs. Nevertheless, PPVs were still moderate, due to low sensitivity, when applying a strict gold standard (sIgE and nasal symptoms). Studies using administrative data must consider how to reliably identify allergic rhinitis, for example, using different data sources, and how a potential misclassification will

impact their results.

Allergic rhinitis is a condition of the upper airways, with a high prevalence worldwide, characterized by symptoms such as nasal obstruction, rhinorrhea, sneezing, and nasal pruritus. This is due to inhaled allergens and respective mucosal inflammation. This review’s objective was to highlight novel mechanisms and treatments of allergic rhinitis to optimize its management.

Proteins such as histone deacetylase (HDAC) and mucin 1 (MUC1) have a role in the epithelial tight junction barrier’s integrity. Inflammatory mediators, such as type 2 innate lymphoid cells (ILC2), myeloid dendritic cells (mDC), and plasmacytoid dendritic cells (pDC), are involved in the development of allergic rhinitis. Other risk factors include genetic susceptibility, age, intrauterine growth restriction, fetal oxidative balance, diet, environmental changes, and essential roles in allergic rhinitis.

Management of allergic rhinitis includes patient education, pharmacotherapy, allergen-specific immunotherapy, and biologics. Novel therapies include highly purified allergens, allergoids, peptides, and new adjuvants for use in specific allergen immunotherapy and specific monoclonal antibodies for blocking the effects of immune mediators.

The gut microbiota has an essential role in the development and regulation of local and systemic immunity. Allergic rhinitis, such as various immune-mediated conditions, has been associated with abnormal gut microbial colonization patterns in children; however, there is not enough data regarding adults. This study aimed to compare the gastrointestinal composition between adults and children who suffer from allergic rhinitis.

This was a cross-sectional study that included 57 adults with allergic rhinitis and 23 healthy controls. Investigators compared samples of their stools via next-generation sequencing of the V3-V4 hypervariable regions of the 16S rRNA gene. Investigators used a reference-based approach with the NCBI database to taxonomic classification and identity approach.

Participants with allergic rhinitis had a significant reduction in species richness. They also had declines in operational taxonomic unit counts and diversity indices. In contrast, they had significantly more Bacteroidetes than healthy controls, as well as an increased abundance of Parabacteroides and a reduced abundance of Oxalobacter and Clostriadiales.

Adults with allergic rhinitis have a different gut microbiome than healthy controls, with reduced microbial diversity and altered abundance of some microbes. Identifying the metabolites and mechanisms underlying the relationship microbiota-host will improve how the gut microbiome composition regulates immunity and may be of interest to potential therapeutic options for allergies.