Tree pollen tends to be the first major irritant ... Some of the most common tree pollens that cause allergies include birch, cedar, cottonwood, maple, elm, oak and walnut, according to the ...

On Tuesday, the Oregon Allergy Associates reported high levels of tree pollen in the air. The dominant pollen was Alder, but tests also picked up Birch, Cedar, Cottonwood, and Hornbeam.