Ah, spring at last. You throw open the window, take a deep breath, and . . . achoo! Your eyes are watering, your throat is itchy, and you’re sneezing your head off. Yep, you’ve got seasonal allergies. The bad news is, scientists say that allergy season is starting earlier and lasting longer. And more people than ever have seasonal allergies—about 81 million just in the U.S. But the good news is that you don’t have to suffer. Here’s all you need to know about what causes seasonal allergies and how to cope.