5 Common Allergens


1
Ragweed
Ragweed can bring sufferers to their knees.
Ragweed can bring sufferers to their knees.
iStockphoto/Thinkstock

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.