Video: How experts put together allergy forecasts

Every spring, microscopic grains of tree, weed, and grass pollen are released en masse, bringing with them an onslaught of seasonal allergies. It’s a busy time of year for both allergists and certified pollen counters, who provide almost daily reports on allergen levels for sniffling locals. Counting pollen requires a patient and discerning eye, but experts David Kerxton and Susan Kosisky have perfected their technique over the past two decades. They walked C&EN through the counting process and answered the question, How bad is this allergy season, really?

Music: “Bright idea” by Geographer, “English Country Garden” by Aaron Kenny, and “Bug catching” by Emily A. Sprague.