Edit. After Black September's assassination of Israeli athletes at the Munich Olympics in 1972, Prime Minister Golda Meir okays a black-box operation to hunt down and kill all involved.
Yellow pollen is produced by evergreen trees, primarily pine trees, including spruce, true cedar trees, fir trees, larch and hemlock. Although yellow pollen looks like it could cause an allergic reaction, in reality it does not trigger allergy symptoms at all. It can stain the skin and clothing, however.
But this relatively big, showy pollen you see from trees and flowers really isnt the culprit. Its the microscopic pollen you dont see that causes allergies. This can be from deciduous trees in the spring such as oak, elm, birch, maple, ash, alder, some pines, box elder, and willow. The hardwoods especially are the culprits.