At roughly 600 species strong, oaks are some of the most familiar trees on Earth — and some of the most allergenic.
Habitat: Northern Hemisphere, from cold latitudes to tropical Asia and the Americas
Description: Sturdy trees, up to 150 feet tall. Oaks can be either deciduous or evergreen, but they're all monoecious.
Allergy season: Spring
Tips: There's little hope of escaping oak trees, and since they're monoecious, you can't just dodge the males. Be sure to at least follow general pollen-avoiding advice, such as keeping windows closed and limiting outdoor activity from 5 to 10 a.m. in the spring. Natural remedies like astralagus root, raw local honey or spicy foods may also offer some relief, but don't expect any miracles.