Interactive effects of allergens and air pollution on respiratory health: A systematic review.

BACKGROUND: Studies have demonstrated an adverse role of outdoor allergens on respiratory symptoms. It is unknown whether this effect is independent or synergistic of outdoor air pollutants. METHODS: We systematically reviewed all epidemiological studies that examined interaction effects between counts of outdoor airborne allergens (pollen, fungal spores) and air pollutants, on any respiratory health outcome in children and adults. We searched the MEDLINE, EMBASE and Scopus databases. Each study was summarized qualitatively and assessed for quality and risk of bias (International Prospective Register for Systematic Reviews, registration number CRD42020162571). RESULTS: Thirty-five studies were identified (15 timeseries, eight case-crossovers, 11 panels and one cohort study), of which 12 reported a significant statistical interaction between an allergen and air pollutant. Eight interactions were related to asthma outcomes, including one on lung function measures and wheeze, three to medical consultations for pollinosis and one to allergic symptoms (nasal, ocular or bronchial). There was no consensus as to which allergen or air pollutant is more likely to interact. No study investigated whether interactions are stronger in atopic individuals. CONCLUSION: Despite strong evidence from small experimental studies in humans, only a third of studies identified significant allergen-pollutant interactions using common epidemiological study designs. Exposure misclassification, failure to examine subgroups at risk, inadequate statistical power or absence of population-level effects are possible explanations.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis.

BACKGROUND: Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR). METHODS: Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus. RESULTS: The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR. CONCLUSION: This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

The influence of sensitisation to pollens and moulds on seasonal variations in asthma attacks.

No large study has described the seasonal variation in asthma attacks in population-based asthmatics in whom sensitisation to allergen has been measured. 2,637 young adults with asthma living in 15 countries reported the months in which they usually had attacks of asthma and had skin-prick tests performed. Differences in seasonal patterns by sensitisation status were assessed using generalised estimating equations. Most young adults with asthma reported periods of the year when their asthma attacks were more common (range: 47% in Sweden to 86% in Spain). Seasonal variation in asthma was not modified by sensitisation to house dust mite or cat allergens. Asthmatics sensitised to grass, birch and Alternaria allergens had different seasonal patterns to those not sensitised to each allergen, with some geographical variation. In southern Europe, those sensitised to grass allergens were more likely to report attacks occurred in spring or summer than in winter (OR March/April 2.60, 95% CI 1.70-3.97; OR May/June 4.43, 95% CI 2.34-8.39) and smaller later peaks were observed in northern Europe (OR May/June 1.25, 95% CI 0.60-2.64; OR July/August 1.66, 95% CI 0.89-3.10). Asthmatics reporting hay fever but who were not sensitised to grass showed no seasonal variations. Seasonal variations in asthma attacks in young adults are common and are different depending on sensitisation to outdoor, but not indoor, allergens.

Assessment of allergen sensitization in a general population-based survey (European Community Respiratory Health Survey I).

PURPOSE: Exposed to a common environment, the IgE-mediated immune response differs, for instance, among sensitized subjects, some of them reacting toward one allergen (monosensitized) whereas others are sensitized to a wide array of allergens (polysensitized). However, a better phenotypic characterization is needed for epidemiologic studies. Using the data collected during the ECRHS I (European Community Respiratory Health Survey), several assessments of skin prick tests and serum-specific IgE to identify mono- and polysensitized patients were compared. METHODS: Subjects took part in the ECRHS-I. The CAP-System was used for serum allergen-specific IgE, and allergen-coated Phazet was used for prick tests. Four allergens (Dermatophagoides pteronyssinus, cat, timothy grass, and Cladosporium) were measured using IgE and nine (the same ones plus olive pollen, birch, Alternaria, Parietaria, and ragweed) were skin tested. One to two local allergens were also tested, depending on countries. RESULTS: Prevalence of sensitization in 11,355 subjects (34.0 [27.9-40.1] years, 49.9% men) ranged from 32.3% (four specific IgE, 19.3% mono- and 13.0% polysensitized) to 41.8% (four specific IgE combined to nine prick tests, 19.6% mono- and 22.2% polysensitized). Concordance between four specific IgE and four prick tests was weak (weighted κ 0.65 [0.64-0.66]). Concordance between seven and nine prick tests was high (weighted κ 0.99 [0.98-1.00]). Local allergens induced small changes in the prevalence of sensitization, and reclassified some subjects from mono- to polysensitized. CONCLUSIONS: Skin tests or serum-specific IgE may be chosen to identify allergenic sensitivity, mono- and polysensitized subjects without being strictly interchangeable.