If I had seasonal allergies when I was younger. Is it possible to grow out of them?

Allergies and aging. Many people grow out of their allergies as they mature. High hormone levels in adolescence sometimes help young people (especially young men) to seem less allergic for several years, and then the allergies may recur, usually in the late 20s. The peak ages for adults to develop allergies are from 25-35. If they're gone, just wait and see.