As always when it comes to natural health: prevention is key!
So for seasonal allergies, I urge you to clean your hands, eyes and nose regularly to prevent pollen from settling in and tickling you.
For example, you can get into the habit of washing your nose every day, once or several times a day, using a seawater spray or, even better, a lota (also known as a neti pot) in which you put room-temperature water, a pinch of salt and 1 teaspoon of tarragon hydrosol.
When you get home, remember to wash your face to remove any pollen residue.
Also remember to wash your hands as regularly as possible, especially when you're out in nature, and avoid touching your face.