Why Does Pollen Make You Sneeze?

Unlike animals, plants are stationary and have to rely on a process called pollination in order to reproduce. Pollen is actually the male reproductive cells present on all flowering plants. Plants with bright flowers, like roses, have larger, waxy pollen and must rely on insects to carry their pollen from one plant to another. Grasses and trees have much smaller, lighter pollen, and those plants rely on wind currents to carry their pollen. While the wind process of pollination works fairly well for the plants, it can cause problems for the humans who inhale it.

Response to Pollen

• Not all people have a negative response to pollen. On a dry, windy day, trees and grasses may release millions of pollen spores into the atmosphere and some people can inhale these spores with little to no reaction at all. If they do have a reaction, they may experience light sneezing, if the pollen counts are very high. This sneezing is a mechanical response to the irritation caused by the pollen in the sinuses. Once the person gets away from the irritant, or clears it from their body, the sneezing stops.

Pollen Allergy

• There are others, however, who have what is known as a pollen allergy. In these people, exposure to even small amounts of pollen initiates an allergic response which includes itching, coughing, watery eyes and, of course, sneezing. In people with pollen allergies, the allergic response does not immediately stop when they remove the source of the allergen. This is because the allergic response is a chemical reaction on the part of the immune system.

The Allergic Response

• In people with pollen allergies, the immune system sees the pollen as a hostile intruder and releases antibodies and chemicals (histamine) to attack the invader. It's the histamines that cause the classic allergy symptoms (like, most obviously, sneezing) and those symptoms will continue as long as the histamines are in the bloodstream. The longer the exposure to the pollen, the more histamine released. So, once the allergic person gets away from the pollen, the symptoms may continue for several minutes or hours, until the histamine is gone.

Relieving Symptoms

• Taking an antihistamine at onset may relieve the symptoms but, for people with severe allergies, even that may not be enough. Most people with pollen allergies take daily histamine blockers as a preventative measure. The daily blockers build up in the system and prevent the histamines from being release or from sitting on the receptors--effectively stopping the allergic reaction before it starts. One interesting thing about pollen allergies is that initial exposure may result in a mild reaction but the reaction gets more severe with repeated exposure. This is why hay fever symptoms often get worse from season to season, and why some medications that worked one year, may not work the next.

Sneezing and Larger Pollen

• It is possible to have an allergic reaction to the larger flower pollen but those reactions are not as common. The pollen is much bigger and not likely to become airborne on its own. So the only way to inhale the pollen is to stick one's nose in the flower or to somehow make the pollen airborne. Still, people do sometimes sneeze in the presence of certain flowers and this may be more of a mechanical response, as a result of sniffing the flower, than a chemical, or allergic, response.