The Future Is Here
We may earn a commission from links on this page

What Pepper Spray Does to Your Body

We may earn a commission from links on this page.

When Lieutenant John Pike casually hosed down a line of seated protesters with pepper spray, a lot of weird stuff immediately followed. No, we're not talking about the evolution of the meme. Or even the nationwide backlash.

We're talking about what happened to the protesters' bodies immediately after they got hit. Pepper spray takes your nervous system out back and beats the holy hell out of it.


The main pain-causing ingredient in most pepper sprays is an oil that comes from the same plant as cayenne pepper. (Don't rub that shit in your eyes either.) But there are actually five major heat-producing elements in the spray that makes up a body-rocking cocktail spraymakers add to a solution containing a propellant. They call it the capsaicinoid concentration. Manufacturers dilute a small percentage of the stuff—usually between 0.18% to 1.33% for human targets. When sealed up in aluminum and nozzled, police have a neurotoxin in a can.

And then it happens: You're minding your own business, sitting in the middle of a road with some friends, and then a cop walks in front of you and turns the world into a source of pain. You gasp as the spray hits your airwaves, causing instant inflammation of the mucous membranes in your throat and nose. The lining of your throat swells—not enough to stop you from breathing, but just enough to make it tough to get your fill of air. Coughing, gagging, and shortness of breath are all to be expected. The stuff also temporarily paralyzes your larynx, making it difficult to speak. Then your mean arterial blood pressure shoots up; blood floods your face, making it appear as if it has been burned. Normal breathing—the calm in-and-out that you don't usually think about—may not return for another 45 minutes.


It doesn't matter if you're wearing glasses or contacts. When the doped propellant hits your eyes, the capsaicinoids stimulate your primary sensory nerve endings, which compel the nerve terminals to cough up their neuropeptides. Neuropeptides are the molecules neurons use to talk to each other, and when the spray forces them out, they cause inflammation.

The pepper can also damage the epithelial cells of the cornea, causing clusters of surface cells to detach. At the same time your eye capillaries dilate, which makes you reflexively jam your eyes shut. Sound bad? Don't worry, you'll have a chance cry about it. Next, of course, come the tears—or rather, the capsicum-induced hypersecretion of water.

Rubbing your face will only make it worse. Splashing lots of cold water will help in that way drinking water helps when you've accidentally chomped a bhut jolokia—it kinda works, but not immediately. Protesters say milk is the best way to fight the sting.

When you think it's finally over, when the intense stinging has stopped: a parting gift. You'll be sensitive to light for about a week.


Sounds bad? It used to be worse. When the fiery concoction was first used in the US in the late 1970s, the percentage of pepper to spray was more severe—as were the effects when you were hit with it. Early versions could force the detachment of the entire corneal epithelium, causing a condition that required medial care for weeks.

We can only hope the UC Davis students make a speedier recovery.

Rachel Swaby is a freelance writer living in San Francisco. Check her out on Twitter.


Giz Explains is where we break down whatever science or tech questions are scratching at the backs of our noggins. Got questions of your own? Email them to us at and we'll see about answering them.

Photo: Spencer Platt