The Origin of the Allergy

Allergies may be an essential component of the immune system.

Allergies are extremely common and the sources of allergies are numerous. Conventional thinking on their cause, however, may be off base.

Immunologist Ruslan M Medzhitov, PhD, thinks allergies may actually be an essential part of the body’s defense system. Conventional thinking is that allergies result when the immune system goes haywire and overreacts to a foreign substance. Dr. Medzhitov thinks that’s incorrect.

Dr. Medzhitov is a professor of immunobiology at Yale University and an investigator at Howard Hughes Medical Institute.

Allergens (the substances that cause allergies) include pollen, gold, latex, medications, insect venom, peanuts, perfume, eggs, salmon, beef, molds and many other substances.

Some people have multiple allergies while others have none. Symptoms can range from minor sniffles and runny eyes to life-threatening anaphylaxis–a severe allergic reaction by the body. Treatments offer limited help, and many of the medications cause side effects like drowsiness.

Dr. Medzhitov has been studying the immune system for more than 20 years and has recently started to ask why people get allergies in the first place.

The current leading theory is that allergies are a misfire originally developed to protect humans from parasitic worms. Since this is a problem not often encountered in developed countries, the immune system reacts to other targets instead.

The immune system produces antibodies in response to an infective agent like bacteria, and the antibodies quickly overwhelm the invader to restore health. With allergies, however, the antibodies overwhelm the body instead of the invader.

Dr. Medzhitov thinks that allergies are a technique the body uses to quickly develop a pattern-recognition system for new threats.

Allergens can cause physical damage to the body and Dr. Medzhitov theorized that an allergic reaction was actually a way to expel the allergen. Most of the major symptoms–runny nose, tears, sneezing, coughing, nausea, vomiting and diarrhea–are ways to get the allergen out of the body.

Dr. Medzhitov and team have tested this theory since 2012. They found that injecting an allergen from honey-bee venom didn’t cause an allergic response unless the allergen damaged cells.

Test animals that had received an initial dose of the honey-bee venom allergen mounted an allergic response when given a second dose. Animals that had not been previously exposed experienced a severe drop in body temperature that was often fatal.

Similar research by another team of scientists confirmed these results.

Dr. Medzhitov thinks allergies are like a home-alarm system that quickly identifies something potentially toxic and readies a defense against another break-in. The allergic response leads an individual to avoid potential toxins, and this can be life-saving.

Dr. Medzhitov and team are now testing mice that have been genetically modified to prevent them from mounting an allergic response. Dr. Medzhitov thinks these animals may not suffer allergies, but will get sick from many other things instead because they will have lost an important protective response.

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