Why the Hell Do We Have Allergies, Anyway?


Pollen should be harmless to us humans. Tiny flower powder that bumble bees carry around in their adorable knee-pockets? Pshh, what harm could that do? But if you’re one of the unfortunate 8% of American adults who suffers from hayfever, you’ll know just what a harbinger of doom it really is. So what the heck is happening in your body that makes it feel like your head is going to explode?

Put simply, allergens like pollen or cat hair put your immune system on the fritz. As the American Academy of Allergy, Asthma and Immunology explains, your body misidentifies these innocuous items as something more dangerous, and sends out antibodies to attack them. Once released, these antibodies cause cells in the affected area to release chemicals—like the itch-inducing histamine—which set off a domino reaction of hives, congestion and seemingly whatever else your body decides it wants to afflict you with that day.

Before you begin cursing your own stupid body, it’s important to note that it doesn’t do this arbitrarily: There actually is a point to histamine, it’s just sometimes used in the wrong circumstances: When used correctly, histamine is one of the body’s front line defences against foreign particles. The problem for you, hayfever sufferer, is that it works by increasing blood flow, which causes swelling. It also causes blood vessel walls to let fluid leak out—this leads to runny noses which irritate the nostrils, hence all that uncontrollable sneezing (gesundheit, you go ahead and wipe down your screen, we’ll wait).

So why do some people have allergies, while others are able to swim in an olympic-sized pool filled with kittens without a care in the world? This is where you can curse your stupid body: It’s really just down to a mistake on the part of your immune system. If, on just one occasion, it mistakes a cat hair for a genuine threat, it creates antibodies in response. Once that error is made, that’s it: It’s going to continue to manufacture those antibodies every single time you come into contact with Mrs. Flufferwiggle’s cast-offs.

Your next question is presumably, how the hell can it think cat hair is dangerous? Well, believe it or not, there is a reasonable answer to that: Your body is tuned to protect itself against parasitic worms, and cat hair molecules are awfully similar in shape to those of a parasitic worm, according to this 2015 study.

Cat hair isn’t the only fake worm in the bunch. All kinds of allergens are mistaken by your body for microscopic parasites: The scientists performing the study mentioned above found 2,445 different parasite proteins similar in size, shape and genetic makeup to the proteins found within common allergens like that oh-so-deadly pollen.

So the next time a patch of dandelions sends you sneezing all the way to Mars, you can at least take comfort in the knowledge that it’s just pollen, and not an infestation of parasitic worms.