What is triggering your allergies?

Brian Handwerk reports at Smithsonian Magazine,

Peanuts. Bees. Pets. Trees. For most people, these things are harmless parts of everyday life. But for allergy sufferers, plenty of seemingly innocuous items can be unbearably irritating and even lethal. Now scientists have uncovered a possible molecular reason why humans evolved to have allergies, and it could lead to new ways to treat the troublesome condition.

Allergies are immune reactions gone wrong that can cause problems from upset stomachs and asthma attacks to deadly anaphylactic shock. While we've gotten pretty good at understanding what triggers allergies and how to mitigate them, researchers have been unsure why we even have allergies in the first place.

A new computer-powered analysis of the proteins involved in allergic responses supports the theory that a natural immune response that evolved to fight parasites is being misdirected in allergy sufferers against otherwise harmless triggers.

Humans have likely cohabitated with parasitic worms for our entire evolutionary history. But during recent decades, such parasites have largely disappeared in parts of the developed world, while allergy rates have risen. The "hygiene" hypothesis, now several decades old, suggests that with no parasites to fight, the immune system doesn't know when to quit and ends up targeting allergens.

Read more here.