Why do some people suffer from allergies and others don't? The answer has to do with histamines—chemicals found in many of the body's cells—that play an important, but sometimes harmful, role in the immune system.

According to Punita Ponda, MD, assistant division chief in the Department of Allergy and Immunology at Hofstra LIJ Health System in Great Neck, NY, "Our immune systems are designed to fight off invaders that may be harmful to us, producing antibodies as a part of the immune response when it encounters these foreign substances."

These antibodies, when paired with their specific antigens, can attach to what are known as mast cells, which release histamines into our system. Histamines do a great job of protecting us from invaders such as parasites and other agents that are universally harmful. By causing symptoms such as coughing, sneezing, and mucus production, they prevent harmful inhaled substances from getting into the lungs. They may also cause stomach upset and diarrhea, which prevent dangerous substances from being absorbed into the digestive system.

In people with allergies, however, histamines are released in response to things that are innocuous to most, such as cat dander, grass cuttings, or certain foods. For some, symptoms are mild and no more than an annoyance that a box of tissues can handle. For others, so much histamine is released that the symptoms become life threatening.

"The body is overreacting to the trigger and causing itself a problem," says Ponda, referring to the cascade of histamines in uncontrolled cases. If severe, this surge of histamines can lead to anaphylaxis—serious breathing difficulties and/or a drastic decline in blood pressure. Anaphylaxis can be fatal if not quickly treated with epinephrine, a remedy that's typically injected into the bloodstream.

If you've got allergies, you're probably familiar with antihistamines—medications that work to counter the effects of histamines in the body. Although they may give relief, Ponda warns they shouldn't be used as a crutch. "Avoidance is the first line of defense."

This may mean having your cat-owning best friend come to your house for movie night, swapping your daily outdoor walk for a treadmill session on high-pollen days, or steering clear of any dish that possibly could contain trigger foods. If antihistamines fail to give adequate relief in the face of allergy triggers, targeted therapies such as inhalers and steroids may be prescribed.

Punita Ponda, MD, reviewed this article.


Punita Ponda, MD. Phone interview 20 January 2014. http://find-a-doctor.northshorelij.com/physician/pediatrics/dr-punita-ponda-md-11312728#.UuEslvso74Y

American Academy of Allergy Asthma & Immunology. "Peak Flow Meter: Tips to Remember." Web. Accessed 7 January 2014. www.aaaai.org/conditions-and-treatments/library/at-a-glance/peack-flow-meter.aspx.

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