Pollen is a powderlike substance consisting of pollen grains from the anthers the of seed plants. Pollens are carried by the wind or insects to cross pollinate other same type of plants for reproduction. Pollen levels are usually highest in the early morning between 5am and 10am.
Pollens that are spread through the air are usually the ones that cause allergic reaction. These include tree pollen, weed pollen and grass pollen. Pollens that are transfered by insects are flowers and usually don't cause allergies.