Tear gas

Tear gas, formally known as a lachrymatory agent or lachrymator (from the Latin lacrima, meaning "tear"), is a chemical weapon that causes severe eye, respiratory, and skin irritation, pain, vomiting, and even blindness. In the eye, it stimulates the nerves of the lacrimal gland to produce tears. Common lachrymators include pepper spray (OC gas), CS gas, CR gas, CN gas (phenacyl chloride), nonivamide, bromoacetone, xylyl bromide, syn-propanethial-S-oxide (from onions), and Mace (a branded mixture).

Lachrymatory agents are commonly used for riot control. Their use in warfare is prohibited by various international treaties. During World War I, increasingly toxic lachrymatory agents were used.

Tear gas works by irritating mucous membranes in the eyes, nose, mouth and lungs, and causes crying, sneezing, coughing, difficulty breathing, pain in the eyes, and temporary blindness. With CS gas, symptoms of irritation typically appear after 20–60 seconds of exposure and commonly resolve within 30 minutes of leaving (or being removed from) the area. With pepper spray (also called "oleoresin capsicum", capsaicinoid or OC gas), the onset of symptoms, including loss of motor control, is almost immediate. There can be considerable variation in tolerance and response, according to the National Research Council (US) Committee on Toxicology.

The California Poison Control System analyzed 3,671 reports of pepper spray injuries between 2002 and 2011. Severe symptoms requiring medical evaluation were found in 6.8% of people, with the most severe injuries to the eyes (54%), respiratory system (32%) and skin (18%). The most severe injuries occurred in law enforcement training, intentionally incapacitating people, and law enforcement (whether of individuals or crowd control).

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