The type of pollen that most commonly causes allergy symptoms comes from plants (trees, grasses, and weeds) that typically do not bear fruit or flowers. These plants produce small, light, dry pollen granules in large quantities that can be carried through the air for miles.

Common plant allergens include:

• Weeds, such as ragweed, sagebrush, redroot pigweed, lamb’s quarters, goosefoot, tumbleweed (Russian thistle), and English plantain.
• Grasses, such as timothy grass, Kentucky blue grass, Johnson grass, Bermuda grass, redtop grass, orchard grass, sweet vernal grass, perennial rye, salt grass, velvet grass, and fescue
• Hardwood deciduous trees, such as oak, ash, elm, birch, maple, alder, and hazel, as well as hickory, pecan, and box and mountain cedar. Juniper, cedar, cypress, and sequoia trees are also likely to cause allergy symptoms.