As such, allergic reactions are an important part of the body's immune defense system. When you are allergic to something, your body's defenses react and produce potent chemicals such as histamine. Histamine is primarily responsible for watery, itchy eyes and many other typical allergic symptoms. It is unclear why some persons develop allergies. About 10 to 20 percent of the population has allergies.
Symptoms can start at any age but children and young adults are more vulnerable to allergies.
Allergens are the substances that cause allergic reactions. The most common allergens are found in our environment. The eyes undergo frequent allergic reactions due to exposure to the environment. Contact ocular allergies can occur after using eye drop medications or contact lens solutions. Animal danders and feathers.