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Background: While the relationship between pollen and respiratory allergies is well‐documented, the role of short‐term pollen exposure in food allergy and eczema flares has not previously been explored. We aimed to investigate these associations in a population‐based sample of children. Methods: We investigated 1‐ (n = 1108) and 6‐year‐old (n = 675) children in the grass pollen season from the HealthNuts cohort. Grass pollen concentrations were considered on the day of testing (lag 0), up to three days before (lag 1‐lag 3) and cumulatively (lag 0–3). Associations between grass pollen and food skin‐prick test reactivity (SPT ≥ 2 mm at age 1 year and ≥ 3 mm at age 6 years), eczema flares, challenge‐confirmed food allergy, reaction threshold to oral food challenges (OFC), and serum food‐specific IgE levels were analyzed using either logistic or quantile regression models. Atopy and family history of allergic disease were considered as potent effect modifiers. Results: Grass pollen at lag 0–3 (every 20 grains/m3 increase) was associated with an up to 1.2‐fold increased odds of food SPT reactivity and eczema flares in 6‐year‐olds. In 1‐year‐olds, the associations were only observed for peanut in those with a family history of food allergy. Increasing grass pollen concentrations were associated with a lower reaction threshold to OFC and higher serum IgE levels in peanut‐allergic 1‐year‐olds only. Conclusion: Increasing grass pollen concentration was associated with increased risk of food SPT reactivity and eczema flares in children. The associations in peanut‐allergic infants may be related to immune activation and/or peanut and grass pollen cross‐reactivity leading to a lower reaction threshold. [ABSTRACT FROM AUTHOR]

Background: Experimental challenge studies have shown that pollen can have early and delayed effects on the lungs and airways. Here, we qualitatively and quantitatively synthesize the evidence of outdoor pollen exposure on various lung function and airway inflammation markers in community‐based studies. Methods: Four online databases were searched: Medline, Web of Science, CINAHL and Google Scholar. The search strategy included terms relating to both exposure and outcomes. Inclusion criteria were human‐based studies published in English that were representative of the community. Additionally, we only considered cross‐sectional or short‐term longitudinal studies which investigated pollen exposure by levels or season. Study quality assessment was performed using the Newcastle‐Ottawa scale. Meta‐analysis was conducted using random‐effects models. Results: We included 27 of 6551 studies identified from the search. Qualitative synthesis indicated associations between pollen exposure and predominantly type‐2 inflammation in both the upper and lower airways, but little evidence for lung function changes. People with ever asthma and/or seasonal allergic rhinitis (SAR) were at higher risk of such airway inflammation. Meta‐analysis confirmed a positive relationship between pollen season, eosinophilia and eosinophil cationic protein (ECP) in people with ever SAR but the results between studies were highly variable. Heterogeneity was reduced after further subgrouping by age, and the forest plots indicated that eosinophilic airway inflammation to outdoor pollen exposure increased with age. Conclusion: Among people with ever asthma and ever SAR, exposure to increased ambient pollen triggers type‐2 upper and lower airway inflammation rather than a non‐specific or innate inflammation. These findings can lead to the formulation of specific pollen immunotherapy for susceptible individuals. Future research should be directed towards investigating lagged associations and effect modifications using larger and more generalized populations. Systematic review registration: CRD42020146981 (PROSPERO). [ABSTRACT FROM AUTHOR]

Background: The association between grass pollen exposure and early markers of asthma exacerbations such as lung function changes and increase in airway inflammation is limited. We investigated the associations between short‐term grass pollen exposure and lung function and airway inflammation in a community‐based sample, and whether any such associations were modified by current asthma, current hay fever, pollen sensitization, age, and other environmental factors. Methods: Cross‐sectional and short‐term analyses of data from the Melbourne Atopy Cohort Study (MACS) participants (n = 936). Lung function was assessed using spirometry. Airway inflammation was assessed by fractional exhaled nitric oxide (FeNO) and exhaled breath condensate pH and nitrogen oxides (NOx). Daily pollen counts were collected using a volumetric spore trap. The associations were examined by linear regression. Results: Higher ambient levels of grass pollen 2 days before (lag 2) were associated with lower mid‐forced expiratory flow (FEF25%‐75%) and FEV1/FVC ratio (Coef. [95% CI] = −119 [−226, −11] mL/s and −1.0 [−3.0, −0.03] %, respectively) and also 3 days before (lag 3). Increased levels of grass pollen a day before (lag 1) were associated with increased FeNO (4.35 [−0.1, 8.7] ppb) and also at lag 2. Adverse associations between pollen and multiple outcomes were greater in adults with current asthma, hay fever, and pollen sensitization. Conclusion: Grass pollen exposure was associated with eosinophilic airway inflammation 1‐2 days after exposure and airway obstruction 2‐3 days after exposure. Adults and individuals with asthma, hay fever, and pollen sensitization may be at higher risk. [ABSTRACT FROM AUTHOR]

Background The association between grass pollen exposure and lung function changes and airway inflammation is limited. We investigated these associations in a community-based sample, and whether any such associations were modified by current asthma, current hay fever, pollen sensitization and age. Methods Cross-sectional analyses of data from the Melbourne Atopy Cohort Study (MACS) participants (n = 936). Lung function was assessed using spirometry. Airway inflammation was assessed by fractional exhaled nitric oxide (FeNO), and exhaled breath condensate pH and nitrogen oxides (NOx). Daily pollen counts were collected using a volumetric spore trap. The associations were examined by linear regression. Results Higher ambient levels of grass pollen 2 days before (lag 2) were associated with lower mid-forced expiratory flow (FEF25-75%) and FEV1/FVC ratio (Coef. [95% CI] = -119 [-226, -11] mL/s and -1.0 [-3.0, -0.03] %, respectively) and also 3 days before (lag 3). Increased levels of grass pollen a day before (lag 1) was associated with increased FeNO (4.35 [-0.1, 8.7] ppb) and also at lag 2. Adverse associations between pollen and multiple outcomes were greater in adults with current asthma, hay fever and pollen sensitization. Conclusions Grass pollen exposure was associated with eosinophilic airway inflammation 1-2 days after exposure and airway obstruction 2-3 days after exposure. Key messages There is a more delayed effect on lung function compared to airway inflammation. Adults with current asthma, hay fever and grass pollen sensitisation are especially vulnerable. [ABSTRACT FROM AUTHOR]

Background Experimental challenge studies have shown that pollen can affect the lungs and airways. Here, we systematically reviewed community-based studies investigating outdoor pollen exposure, lung function and/or airway inflammation. Methods Four online databases were searched. The search strategy included terms relating to both exposure and outcomes. Inclusion criteria were studies published in English that were representative of the community. We only considered cross-sectional or short-term longitudinal studies which investigated pollen exposure by levels or season. Study quality assessment was performed using the Newcastle-Ottawa scale. Meta-analysis was conducted using random-effects models. Results We included 27 of 6,551 studies identified from the search. Qualitative synthesis indicated associations between pollen exposure and predominantly type-2 inflammation in both the upper and lower airways, but little evidence for lung function changes. People with ever asthma and/or seasonal allergic rhinitis (SAR) were at higher risk of such airway inflammation. Meta-analysis confirmed a positive relationship between pollen season and eosinophilic airway inflammation in people with ever SAR but the results between studies were highly variable. Heterogeneity was reduced after further subgrouping by age and the forest plots indicated that eosinophilic airway inflammation to outdoor pollen exposure increased with age. Conclusion Among people with ever asthma and ever SAR, exposure to increased ambient pollen triggers type-2 airway inflammation rather than a non-specific or innate inflammation. Key messages This review indicates pollen exposure influences predominantly type-2 airway inflammation, but little evidence on lung function. [ABSTRACT FROM AUTHOR]

Thunderstorm asthma is defined as epidemics of asthma occurring shortly after a thunderstorm. While grass pollen has been implicated in thunderstorm asthma events, little is known about the role of fungi and studies have not been synthesised. This systematic review aims to evaluate whether grass pollen is necessary in thunderstorm asthma events and whether fungi also play a part in these associations. We conducted a systematic search using six electronic databases (i.e. CINAHL, Medline (Ovid), Web of Science, ProQuest Central, EMBASE and Google Scholar) and checked reference lists. The search terms used were pollen AND thunderstorm* AND asthma. The inclusion criteria were studies published in English with original human data relating to outdoor pollen and thunderstorm asthma. Twenty of 2198 studies were eligible. Reported findings differed due to variation in methodological approaches and a meta-analysis was not possible. Nonetheless, of the 20 studies included, 15 demonstrated some relationship with nine demonstrating lagged effects up to four days for increasing grass pollen counts associated with increased risk of thunderstorm asthma. Of the 10 studies that examined fungi, nine demonstrated a positive relationship with thunderstorm asthma. The fungal taxa involved varied, depending on whether measurements were recorded before, during or after the thunderstorm. Nevertheless, none of the studies considered fungi as a potential effect modifier for the pollen-thunderstorm asthma association. We found evidence to suggest that grass pollen was a necessary factor for thunderstorm asthma but there are other as yet unrecognised environmental factors that may also be important. Further research is required to examine the role of fungi and other environmental factors such as air quality as potential effect modifiers of the association. • Grass pollen is most commonly associated with thunderstorm asthma. • There is a lagged effect of up to four days. • Grass pollen on its own is not enough to cause thunderstorm asthma. • Fungi is also important, but more studies are required. [ABSTRACT FROM AUTHOR]