Tear gas is effective at dispersing crowds because its key ingredient — called 2-chlorobenzalmalononitrile — triggers the activation of huge numbers of pain receptors in the eyes, as well as irritation in the throat and difficulty breathing. This causes a person's eyes to start tearing and closing involuntarily, effectively incapacitating that person within seconds.
A large number of people in Ferguson — including an eight year-old boy and a group of journalists — have suffered from these symptoms, and there are various photos showing them using a number of different remedies (such as milk and water) to treat tear-gas exposure.
But the unfortunate truth is that effectively treating exposure to tear gas is very difficult, and the best protections and remedies are solely in the hands of medical professionals. Even worse, we still know virtually nothing about the gas' long-term effects. Here's a rundown of what researchers have discovered about dealing with the effects of tear gas:
1) Most makeshift masks don't work perfectly
The most effective defense against tear gas is a gas mask. But gas masks and filters aren't easily available to civilians.
Some protestors have often used a pair of goggles and a wet bandana worn over the mouth to minimize the tear gas' effects on the respiratory system (historically, protesters have used bandanas soaked in lemon juice, cider vinegar, Coca-Cola, or other acidic solutions, though it's not proven that this is more effective). These measures won't fully protect someone by any means, but they can temporarily reduce the amount of tear gas entering the body, giving a person a few extra moments to escape.
2) The best step is usually to leave the area
Once someone has been exposed to tear gas — whether wearing protection or not — the best thing to do is to get out of the gas-filled area as soon as possible. Simultaneously, experts recommend that victims cough, spit, and blow their noses in an attempt to get as much of the chemical out of their bodies as soon as possible.
People with conditions that make them especially vulnerable to tear gas — such as asthma, other respiratory diseases, or immune system disorders — as well as infants and the elderly should seek professional medical help immediately.
3) Victims' eyes need to be washed out thoroughly
Once in a secure location, it's crucial for anyone exposed to tear gas to wash out their eyes thoroughly until the symptoms begin to subside. If the person is wearing contacts, they need to be removed and thrown away.
Protestors in Ferguson have sometimes been using milk as a rinse — and victims of tear gas in other protests around the world have used a variety of remedies, such as lemon juice or a mix of Maalox (or other antacid) and water. But these treatments haven't been clinically tested, so it's hard to say if they're better than water, which is still the rinse proven most effective in clinical trials.
(There is also a chemical called diphoterine that has been shown to be a more effective rinse and is sometimes used in emergency rooms, but it's not widely available apart from medical supply companies.)
4) Longer-term care is often necessary
Apart from tearing and involuntarily blinking, tear gas also causes a longer-term inflammatory response in a person's eyes and skin — and this can take a few days to subside. Initially, it's recommended that victims take cold showers, because warm water can open up a person's pores, allowing further tear gas particles to enter.
Afterward, any piece of clothing or object that was exposed to the tear gas needs to be thoroughly washed or thrown away. Structures hit by tear gas need to be similarly decontaminated of residue, a process that's especially difficult if tear gas has been deployed indoors.
The long-term effects of tear gas on people have barely been studied and are essentially unknown.