Summer's virtually here, which means soon many of us will be incapacitated through sneezes, coughs, and itchy eyes. While allergies are a pain in the ass, they may not be the misguided immune responses many scientists have believed them to be. In fact, a new theory is emerging which suggests that they may have evolved to protect us.
Many immunologists think that allergies to everything from peanuts to pollen are just misdirected bodily responses, the type that's typically directed at parasites. The result is an attempt to purge the body of the non-existent invaders—by sneezing, coughing, itching, and everything else that happens right before you reach for the Benadryl.
But a researcher from Yale University has a different idea. Ruslan Medzhitov points out that parasites and the substances that trigger allergies, called allergens, have nothing in common—so why on Earth should the body react in the way most immunologists suggest?
Instead, he thinks that allergies are an evolved trait, which help protect humans from toxic substances in our surroundings. Writing in an article published in Nature, he explains:
"How do you defend against something you inhale that you don't want? You make mucus. You make a runny nose, you sneeze, you cough. Or if it's on your skin, by inducing itching, you avoid it or you try to remove it by scratching it."
And he's got the evidence to back that up. Some allergic responses, for instance, seem to degrade and detoxify snake and bee venom, while others seem to prevent pests from biting or stinging again. It makes sense that such a response should be preferential evolutionarily.
His argument doesn't necessarily contradict the hygiene hypothesis, which suggests that kids growing up on farms are less likely to develop allergies. That theory rests on a fundamental and direct change in immune response, which trumps the class of allergic reactions—so the two ideas can happily coexist.
Whether the theory turns out to be adopted by the entire scientific community remains to be seen. But in the meantime, take solace in the fact that your allergy might actually put you at an evolutionary advantage over your non-suffering friends. [Nature via Scientific American]
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