The type of pollen can determine whether or not people will be allergic to them. Many of the pollens that cause hay fever come from weeds, trees and grasses. These pollens are comparatively smaller, lighter and drier than other types and are carried easily by the wind.

Heavier pollens, such as the large, waxy pollens found in roses, are carried by insects from flower to flower. Because of their size, fewer can be carried by the wind and they are therefore less likely to cause an allergic reaction in most people. However, people who have prolonged, close contact with colorful and/or scented flowers, such as florists, are more likely to develop allergies to these plants.

Pollens that are most likely to cause allergies in the general public include the following: