What Are Allergies, Anyway?

According to the American College of Allergy, Asthma & Immunology, as many as 50 million people in the United States suffer from allergies. But what are allergies? Why do some people only experience coughing and sneezing once a year, while others must carry an epinephrine auto-injector (EpiPen) everywhere they go? And why do pills and nasal sprays work well to treat some allergies but not at all for others? The answers to these questions were only recently discovered.

What Are Allergies?

The word "allergy" itself was only invented a little more than 100 years ago. Back then, the term "allergy" referred to something that caused an "altered reaction" in the body, but it wasn't understood how allergies worked or what caused them. Sir Henry Dale, M.D., is credited with launching the pursuit for this knowledge because of his research into histamine -- a key chemical involved in an allergic reaction -- and its effects on the body. Scientists expanded on this research throughout the 1900s, examining how red spots from vasodilatation were a histamine response, leading up to the discovery that an allergic reaction can lead to physical shock, and eventually the development of antihistamines -- medicines to counteract histamine's effect on the body during an allergic reaction.

Old Illness, New Understanding

By the year 2000, it was understood that when cells "overreact" to pollen, peanuts, or animal dander, they're carrying out normal processes that the body uses to try to protect itself from infection and exposure to dangerous forces in the environment. The problem isn't that cells aren't working; they're actually working way too well! The body's immune system was designed to fight off viruses, bacteria, and parasites. When it thinks it has discovered something harmful, the body unleashes histamines from immune cells to try and neutralize the danger. Sometimes that helps, and sometimes it hurts.

A small amount of histamine causes a runny nose, itchy eyes and skin, and sneezing. A larger amount may cause the passages in the lungs to tighten, making breathing more difficult, which is called wheezing. If a very large amount of histamine is released, many airways in the lungs, neck, and face can close up, which is called anaphylaxis. The best way to help someone with anaphylaxis is to open up those passageways again quickly using the medicine inside an EpiPen. Other symptoms, like wheezing, coughing, and sneezing, can all be improved by antihistamines, which tell your body not to overreact, or steroids, which calm down the immune system itself.

Today, immune overreactions are common; allergies are the sixth leading cause of chronic illness nationwide. How much medicine you take for your allergies, what kind of medicine works for you, and when to use it all depend on what makes your particular body overreact. Whether it's foodborne, caused by an insect, or carried by the wind, your doctor can help you and your family learn about what allergens affect you and what to do to prevent or treat an allergy.