Synergistic Effects of Air Pollutants and Pollen in Nonallergic Rhinitis

Ragweed pollen
What are the cross-sectional seasonal effects of pollen and air pollutants on nonallergic rhinitis, and what relationships exist between these triggers?

The interaction of pollen with air pollutants may cause a greater adverse reaction among patients with symptoms of nonallergic rhinitis (NAR) than pollen or air pollutants alone, according to study findings published in Journal of Asthma and Allergy.

The global prevalence of chronic rhinitis approaches 30%, and NAR may affect up to half of those with chronic rhinitis. Patients with NAR have more severe rhino-conjunctivitis symptoms during pollen season that in other seasons. There is a paucity of data on the role of pollen and air pollutants on NAR severity. Researchers in China sought to evaluate cross-sectional effects of pollen and air pollutants on patients with NAR across pollen and non-pollen seasons.

The researchers conducted a retrospective real-world cross-sectional study that included 2411 first-visit outpatients with chronic rhinitis who visited the Otorhinolaryngology and Allergy Department of Beijing TongRen Hospital, China, between January 2018 and December 2019. Patients averaged just under 35 years of age, with just over 45% women and 4% individuals with asthma.

Chronic rhinitis was defined by 3 or more nasal symptoms — including but not limited to sneezing, nasal congestion, rhinorrhea, and itching — for more than 12 weeks. A negative allergen test measured by serum-specific immunoglobulin E using a spread of aeroallergen mixture (weed/grass pollen, molds, trees, house dust mites, and animal dander) was used to diagnose NAR. Patients with upper respiratory infections and chronic rhinosinusitis were excluded. Rhino-conjunctivitis symptom scores measured the severity of NAR.

Researchers found that greater exposure to nitrogen dioxide, sulfur dioxide, particulate matter 2.5 micrometers and smaller (PM2.5), and PM10, as well as to pollen concentration during pollen season increased the severity of symptoms in the group of patients with NAR who already had high severity, compared with those patients in the low-moderate severity group. The low-moderate severity group was more susceptible to ozone exposure than the high severity group (OR = 0.828; 95% CI, 0.711-1.339). Researchers noted that during non-pollen seasons, they observed no significant association between the severity of NAR symptoms and pollen concentration or air pollutants. Stratifying different ambient pollutants resulted in different exposure-severity effects.

Study limitations include its retrospective and cross-sectional nature, as well as misclassification of patients.

The “[s]ynergistic effect of pollen and air pollutants, including PM2.5, PM10, SO2, NO2, and O3, might be responsible for aggravating the symptoms of NAR patients during pollen seasons,” the researchers concluded. “[I]t is essential to protect NAR patients from pollen, especially during the pollen seasons,” said study authors, who added that “air pollution needs to be better controlled.”


Huang Y, Zhang Y, Wang J, et al. Impact of air pollutants and pollen on the severity of nonallergic rhinitis: A data-oriented analysis. J Asthma Allergy. Published online August 6, 2022. doi:10.2147/JAA.S372927