Pollen levels show significant diurnal variation, according to findings of a study presented at the ongoing 2022 Annual Scientific Meeting of the American College of Allergy, Asthma and Immunology (ACAAI) being held in Louisville, Kentucky.

Researchers estimated the hourly levels of tree pollen in three sites of Atlanta, a city in the United States in the state of Georgia using an automated sensor for one week between March 24 and March 31, 2021. Results showed that the levels were lower in the morning and gradually started to rise and peaked in late evening. The highest pollen levels occurred between 2 pm to 9 pm, while the pollen levels were lowest between 4 am and 12 noon.

Aside from other measures adopted to avoid or reduce exposure to pollen when allergies are prevalent, it is also important to be aware of the best time to be outdoors when pollen levels are minimum and plan their outdoor activities accordingly, which as per the findings of this study is in the early hours of morning. However, weather and temperature may also affect the pollen levels.

References

1. Lowest pollen counts occur between 4:00 a.m. and noon.  Published Nov. 10, 2022. https://annualmeeting.acaai.org/2022/lowest-pollen-counts.cfm.
2. https://www.healio.com/news/allergy-asthma/20221110/pollen-counts-lowest-earlier-in-day-making-it-best-outdoor-time-for-those-with-allergies, November 11, 2022.