Airborne grass (Poaceae) pollen measurements are used in public warning systems to inform people about the risk of allergic symptoms. However, there is no consensus about which exact thresholds of pollen concentrations provoke the allergic symptoms. The aim of this study was to review the relevant scientific information on the relationship between grass pollen concentrations and the occurrence of emergency department (ED) visits, hospital admissions (HA), drug consumption and allergic symptoms. Literature search was conducted by experts’ consultation and snowball strategy. Studies meeting the criteria for inclusion were assessed regarding their risk of bias (RoB). A high RoB resulted in exclusion of the study from data synthesis. Extensive data were extracted and qualitatively compared. The review is registered in PROSPERO. 32 Studies were eligible while 18 showed a low RoB and were qualitatively synthesised. Emergency department visits and hospital admissions were mostly investigated. Threshold values of 10 grains/m³ and 12 grains/m³ were reported for ED visits and HA. Evidence exists that an increase of 10 grains/m³ of air leads to a significant increase in adverse health outcomes. Especially at a three-day lag, adverse health effects were shown. Variations in exposure and outcome measurement make the definition of pollen thresholds difficult. As a consequence, no defined pollen threshold values could be identified. Studies with uniform exposure measures and statistical methods are necessary to gain a better understanding of the impact of grass pollen on human health. Determining personal thresholds could be beneficial for affected people.

空气传播的禾本科（Poaceae）花粉测量值用于公共预警系统，以告知人们过敏症状的风险。然而，对于哪个确切的花粉浓度阈值会引起过敏症状，目前还没有达成共识。本研究的目的是回顾有关草花粉浓度与急诊科 (ED) 就诊、住院 (HA)、药物消耗和过敏症状发生之间关系的相关科学信息。文献检索采用专家咨询和滚雪球策略。对符合纳入标准的研究进行偏倚风险 (RoB) 评估。高 RoB 导致该研究被排除在数据合成之外。提取了大量数据并进行了定性比较。该评论已在 PROSPERO 中注册。32 项研究符合条件，而 18 项研究显示出较低的 RoB 并进行了定性综合。主要调查急诊科就诊和住院。10 粒/米的阈值ED 访问和 HA 报告了³和 12 粒/m ³。有证据表明，空气每增加 10 粒/m ³会导致不良健康结果显着增加。特别是在三天的滞后时，显示出不利的健康影响。暴露和结果测量的变化使得花粉阈值的定义变得困难。因此，无法确定定义的花粉阈值。为了更好地了解草花粉对人类健康的影响，需要采用统一的暴露措施和统计方法进行研究。确定个人阈值可能对受影响的人有益。