For simplicity's sake, the tear gas we’re talking about here are the grenades that spread a fog of irritating man-made chemicals that cause a painful reaction in the eyes, nose, mouth, and skin. The compounds in the tear gas have changed over the years, with some more toxic than others, but soldiers and civilians alike have been subjected to it for more than 100 years.
These days it’s almost always civilians. The Geneva Protocol of 1925 banned tear gas as a weapon of war, which nearly every country in the world subsequently claimed to respect and uphold. The 1993 Chemical Weapons Convention, ratified by all but four UN member states, required nations to renew that promise with an enormous caveat: Tear gas could be used by police states as a nonlethal method of quelling "rioters." Police departments around the United States possess huge quantities of this stuff, and they toss it around liberally, as anyone following the news for the past few days has seen.
Wear goggles and sunscreen, not contacts.
Saba and Odhner agree on a few key items. A big one? Do not wear contacts to a protest. "Your eyes will reflexively shut as a reaction to the pain, and it'll be very hard to get the contacts out," Odhner says. As you're doing that, you'll have tear gas on your hands too.
To avoid taking the brunt of a chemical attack, wear goggles—even swimming goggles—no matter how dorky they look. They can make a huge difference. Tear gas burns the skin, so the more skin you can cover up, the better. Odhner recommends wearing a long-sleeve shirt you don't care about, one you're prepared to toss if it ends up in the path of tear gas. Tear gas also hits harder when you're sunburned, so wear sunscreen too (non-oil-based options are best). "There's nothing worse than tear gas on a sunburn, which I can certify from experience," he says. Pack tissues and, if you're asthmatic, bring your inhaler.
Finally, it’s good to have at least a few water bottles or saline solution, in case you need to flush your eyes or another person’s eyes. The goal is a gentle, constant stream of water, which is hard to achieve with a bottle that has a large opening—dedicated eye-flush bottles are available, but a sports bottle also works well, as does a water bottle with a small hole poked into the top.
Don't bother with milk.
There's little evidence proving that any substances beyond water and sterile saline can alleviate the body's response to tear gas. One study disproved baby shampoo's effectiveness. People have long assumed milk is useful, and Odhner says it's relatively harmless, but not any better than water. He says 10 years ago, protesters thought apple cider vinegar would protect them, but "the people we treated didn't seem subjectively any better off than those who didn't use apple cider vinegar." Occupy Wall Street protesters swore by antacids.
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