When exactly “allergy season” strikes depends on what you’re allergic to, but for many people, it’s in the spring, when the air fills with pollen from trees and other plants. But why does pollen make you sneeze?
Since humans have coexisted with plants for our entire history, you might think we’d be better at dealing with pollen. However, each year, pollen still causes sneezing and other allergic reactions in lots of people. Here’s the reason for your sneezing!
What Is Pollen?
Pollen allows plants to reproduce: male plants produce it to fertilize female plants. However, for this powdery substance to work, it has to get from the male plants to the female plants. This transfer process is how pollen ends up in your nose, making you sneeze.
All kinds of plants, from flowers and trees to grasses and weeds, produce pollen. However, not all types of pollen tend to produce allergies. Most plants with colorful flowers rely on insects, such as bees, to carry their pollen from plant to plant. Since that pollen is always attached to an insect or a plant, it can’t get into your nose and trigger allergies.
However, other kinds of plants use the wind to spread their pollen around. This pollen is lightweight, so it can easily travel by air. You’ll often breathe in this airborne pollen during spring when plants are pollinating, causing an allergic reaction.
This also explains why you often sneeze more when it’s breezy and dry since lots of pollen is floating in the air. When it rains, the wet pollen can’t fly around and into your nose.
What Happens When Pollen Enters Your Nose?
So, why does pollen make you sneeze once you inhale it?
Inside your nose is mucus. Although it seems gross when it comes out of your nose (such as when you sneeze), mucus is vital for your health. This barrier traps dirt and debris before it gets into your lungs, and helps keep you from getting sick. Pollen is just one of the things that get trapped by mucus.
However, a pollen allergy will cause inflammation in your nose after pollen enters: this is called rhinitis. Other things can cause rhinitis, too—you experience it whenever you have a cold, for example.
In addition to making you sneeze, allergic rhinitis can make you congested, make your nose run or itch, and cause other unpleasant symptoms.
These symptoms are the result of an immune system reaction. Your immune system is your body’s defense system. When you have allergies, your immune system sees something harmless, like pollen, as a threat. So, if you have a pollen allergy, your immune system reacts to pollen in your nose as though it were a dangerous invader—even though it’s not really dangerous.
This immune system overreaction causes allergic rhinitis, with all its sneezing and other symptoms. When you sneeze due to pollen allergies, that’s your body trying to get the “dangerous invader” out of your nose.
Why Doesn’t Everyone Have Allergies?
Not everyone is allergic to pollen, and not everyone is allergic to the same kind of pollen. Why is that?
Scientists aren’t quite sure of the answer to that question—because they don’t yet understand why we get allergies in the first place. After all, these immune-system overreactions harm us, rather than helping us, so it doesn’t really make sense that they’re so widespread.
According to one theory, allergies are a result of the body’s natural defense against parasites, gone awry. However, another theory is that allergies are our defense against toxins instead. In the past, some types of pollens could have really been dangerous, which might be why many people’s bodies still see them as a threat.
For now, though, we don’t fully understand why allergies of any kind exist, or why they’re so widespread. We just know that for some reason, some people’s bodies see harmless allergens like pollen as dangerous. The immune system kicks in and does anything it can to get rid of the pollen, like making you sneeze and giving you a runny nose.
Of course, the experience of a pollen-induced sneezing fit still isn’t enjoyable. But it’s actually evidence of your immune system trying to protect you—a trait that may have helped humans survive thousands of years ago when our bodies were assailed by now-forgotten threats.