3. You catch a cold at the wrong time.
Some research shows that viral infections can lead to allergies.
"Certain viruses can sort of get your immune system going," Jain says. "If this happens at the wrong time and you're exposed to pollen at the wrong time, it might turn on the genes that are tied to allergies."
You don't need to contract a rare disease for that switch to be flipped. The rhinovirus, which causes the common cold, could be enough to kick start the process.
4. You're around a lot of pollution.
While the particles in the air might irritate you, that's only part of the problem.
Pollen in very polluted areas may produce greater amounts of proteins that cause allergic reactions.
Air pollution might also help pollen particles scatter through the air. That makes them easier to inhale.
If you think you have allergies, try to figure out what you are allergic to so you can avoid it. It’s OK to talk to your pharmacist about which over-the-counter medicine may work for you. But if you need more help, follow up with your doctor or see an allergist for testing, Jain says.
If you have moderate or severe allergies, you should also consider immunotherapy, Sublett says. This treatment involves getting allergy shots (or taking tablets) that include a tiny bit of an allergen so that your body eventually becomes less sensitive to it.