Allergies are extremely common, with symptoms ranging from mild to severe and even life-threatening. Any allergic reaction to a substance, whether it's a food, pollen, pet, or a medication, begins when your immune system mistakes an ordinary substance for a dangerous enemy.
The immune system is designed to repel harmful invaders such as bacteria or viruses. It mobilizes to flag the invading organisms by producing Immunoglobulin E (IgE) antibodies which then call other body chemicals to the scene to fight off the invaders and sweep them up. In an allergic reaction, these chemicals cause the symptoms you feel on your skin, or in your airways, or digestive tract.
It's important to understand that people with allergies can live healthy, active lives once they know and understand what triggers their reactions. Effective medications can prevent or lessen symptoms. Those whose reactions are life-threatening can carry medication to reverse the allergic process, giving them time to seek emergency medical care.