This spring, pollen from blooming trees and plants will join other allergens in affecting over 45 million Americans, causing itching eyes, sneezing, nasal stuffiness, Nasal congestion and drainage, and sometimes headache. This year, some areas are reporting record-high pollen counts, which are sure to impact the people breathing that yellow, dust-like allergen.

Some people may experience hearing changes, scratchy sore throats, hoarseness, and cough. In the most serious situations, allergies can lead to balance disturbances, swelling in face or throat tissues, skin irritations, and even respiratory problems and asthma.

More carbon dioxide pollution encourages plant growth, which means more ragweed and tree pollen. In fact, the ubiquitous weed makes nearly twice as much pollen now as it did 100 years ago and will likely double its production again over the coming century with predicted increases in carbon dioxide levels, according to a U.S. Department of Agriculture study.