Asthma Hospitalization Risk in Children From Grass, Weed, and Other Pollens

Grass, other weeds, and unclassified pollen were significantly associated with increased risk for asthma hospitalization in young children.

Children ages 2 to 5 years and boys are more vulnerable to asthma exacerbations due to pollen than older children and girls, according to an article published in Clinical and Experimental Allergy.

Researchers assessed the role that different pollen types played in asthma hospitalizations for children and adolescents in Sydney, Australia, from May 1, 2008, to May 31, 2013. A study sample of 2098 children and adolescents (ages 2 to 18 years) hospitalized for asthma exacerbations at three different Sydney hospitals were included.

Data on pollen concentrations (expressed as grains per cubic meter) were obtained with a 7-day Burkard volumetric spore trap located on the roof of Campbelltown Hospital. The pollen grains were classified into 8 categories: grass, Plantago, other weeds (Parietaria pollen and Echium plantagineum), and pollen from Platanus, conifer, EucalyptusCasuarina, or Cupressus trees. Total pollen, total tree, and unclassified pollen categories were also created.

During the study time period, 929 children (44.3%) were admitted during the first pollen peak (January to April), 450 (21.5%) during the second pollen peak (July to October), and 719 (34.3%) during the other months of the year. Grass, other weeds, and unclassified pollen were significantly associated with increased risk for asthma hospitalization (odds ratio [OR],1.037; 95% CI, 1.005-1.070; OR, 1.053; 95% CI, 1.009-1.098; and OR, 1.034; 95% CI, 1.010-1.058; respectively). 

Related Articles

When the data were sex stratified, a trend showed an additional risk for asthma hospitalizations in boys due to grass and unidentified pollens (OR, 1.046; 95% CI, 1.003-1.090 and OR, 1.041; 95% CI, 1.010-1.073, respectively). With age stratification, children ages 2 to 5 were at an additional risk for asthma hospitalizations due to grass (OR, 1.047; 95% CI, 1.005-1.091), Platanus (OR, 1.017; 95% CI, 1.003-1.032), other weeds (OR, 1.075; 95% CI, 1.024-1.129), and unclassified pollens (OR,  1.059; 95% CI, 1.027-1.091).

Study investigators concluded that there is “evidence that different species of pollen are important triggers of asthma exacerbations. These factors are important for urban planning and greening cities. In countries with varying climatic conditions and different pollen species, standardized national pollen monitoring with advanced warning systems could assist patients at risk [for] pollen induced asthma exacerbations.”


Shrestha SK, Katelaris C, Dharmage SC, et al. High ambient levels of grass, weed and other pollens are associated with asthma admissions in children and adolescents: A large 5-year case-crossover study [published online July 5, 2018]. Clin Exp Allergy. doi:10.1111/cea.13225