Named for the  ragged shape of its leaves, ragweed is the most common plant allergen—and a most tenacious weed! A single plant can produce a million grains of pollen in a single day and a billion grains during its growing season. And that pollen is made for roaming. Samples have been collected 400 miles out to sea and up to two miles in the air.

Unlike many other seasonal allergens, ragweed begins pollinating in late summer, around mid-August, and continues until a heavy frost. Seventy-five percent of people who are allergic to pollen are allergic to ragweed—a member of the Compositae family—which also includes sage, burweed marsh elder, rabbit brush, mugworts, groundsel bush and eupatorium. People with ragweed allergy may also get symptoms when they eat cantaloupe and banana. Chamomile tea, sunflower seeds and honey containing pollen from Compositae family members occasionally cause severe reactions, including shock.