One in three people in the U.S. experience allergies, making them one of the most common chronic conditions. Allergies happen when your immune system mistakenly identifies a normally harmless substance as a threat and responds to it. These substances, known as allergens, may be inhaled, eaten, or encountered through physical contact. Each season brings new pollen threats for seasonal allergies. In North Carolina, tree pollen accounts for seasonal allergies in spring, grass pollen in ...