Tear Gas
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Tear Gas

Tear gas in use in France in 2007
Exploded tear gas canister on the fly in Greece

Tear gas, formally known as a lachrymator agent or lachrymator (from the Latin lacrima, meaning "tear"), sometimes colloquially known as mace,[NB 1] is a chemical weapon that causes severe eye and respiratory pain, skin irritation, bleeding, and blindness. In the eye, it stimulates the nerves of the lacrimal gland to produce tears. Common lachrymators both currently and formerly used as tear gas include pepper spray (OC gas), PAVA spray (nonivamide), CS gas, CR gas, CN gas (phenacyl chloride), bromoacetone, xylyl bromide and Mace (a branded mixture).

While lachrymatory agents are commonly deployed for riot control by law enforcement and military personnel, its use in warfare is prohibited by various international treaties.[NB 2] During World War I, increasingly toxic and deadly lachrymatory agents were used.

Exposure to tear gas agents may produce numerous short-term and long-term health effects, including development of respiratory illnesses, severe eye injuries and diseases (such as traumatic optic neuropathy, keratitis, glaucoma, and cataracts), dermatitis, damage of cardiovascular and gastrointestinal systems, and death, especially in cases with exposure to high concentrations of tear gas or application of the tear gases in enclosed spaces.[1]


2-chlorobenzalmalononitrile is the active agent in CS gas.

Tear gas generally consists of aerosolized solid or liquid compounds (bromoacetone or xylyl bromide), not gas.[2] Tear gas works by irritating mucous membranes in the eyes, nose, mouth and lungs. It causes crying, sneezing, coughing, difficulty breathing, pain in the eyes, and temporary blindness. With CS gas, symptoms of irritation typically appear after 20 to 60 seconds of exposure[3] and commonly resolve within 30 minutes of leaving (or being removed from) the area.[4] With pepper spray (also called "oleoresin capsicum", capsaicinoid or OC gas), the onset of symptoms, including loss of motor control, is almost immediate.[4] There can be considerable variation in tolerance and response, according to the National Research Council (US) Committee on Toxicology.[5]

The California Poison Control System analyzed 3,671 reports of pepper spray injuries between 2002 and 2011.[6] Severe symptoms requiring medical evaluation were found in 6.8% of people. The most severe injuries were 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).[6]


As with all non-lethal or less-lethal weapons, there is some risk of serious permanent injury or death when tear gas is used.[7][8][2] This includes risks from being hit by tear gas cartridges that may cause severe bruising, loss of eyesight, or skull fracture, resulting in immediate death.[9] A case of serious vascular injury from tear gas shells has also been reported from Iran, with high rates of associated nerve injury (44%) and amputation (17%),[10] as well as instances of head injuries in young people.[11]

While the medical consequences of the gases themselves are typically limited to minor skin inflammation, delayed complications are also possible. People with pre-existing respiratory conditions such as asthma are particularly at risk. They are likely to need medical attention[3] and may sometimes require hospitalization or even ventilation support.[12] Skin exposure to CS may cause chemical burns[13] or induce allergic contact dermatitis.[3][4] When people are hit at close range or are severely exposed, eye injuries involving scarring of the cornea can lead to a permanent loss in visual acuity.[14] Frequent or high levels of exposure carry increased risks of respiratory illness.[2]

In the 2019-20 Chilean protests various people have suffered complete and permanent loss of vision in one or both eyes as result of the impact of tear gas grenades.[15][16][17]

Site of Action

TRPA1 ion channels expressed on nociceptors have been implicated as the site of action for CS gas, CR gas, CN gas (phenacyl chloride) and bromoacetone in rodent models.[18][19]



During World War I, various forms of tear gas were used in combat and tear gas was the most common form of chemical weapon used. None of the belligerents believed that the use of irritant gases violated the Hague Convention of 1899 which prohibited the use of "poison or poisoned weapons" in warfare. Use of chemical weapons escalated during the war to lethal gases, after 1914 (during which only tear gas was used).

The US Chemical Warfare Service developed tear gas grenades for use in riot control in 1919.[20]

Use of tear gas in warfare, as with all other chemical weapons, was prohibited by the Geneva Protocol of 1925: it prohibited the use of "asphyxiating gas, or any other kind of gas, liquids, substances or similar materials", a treaty that most states have signed. (Police and civilian self-defense use is not banned in the same manner.) [21]

Tear gas was used in combat by Italy in the Second Italo-Ethiopian War, by Japan in the Second Sino-Japanese War, Spain in the Rif War and by the United States in the Vietnam War.[22]

Tear gas exposure is an element of military training programs, typically as a means of improving trainees' tolerance to tear gas and encouraging confidence in the ability of their issued protective equipment to prevent chemical weapons exposure.[23][24][25]

Riot control

Certain lachrymatory agents, most notably tear gas, are often used by police to force compliance.[8] In some countries (e.g., Finland, Australia, and United States), another common substance is mace. The self-defense weapon form of mace is based on pepper spray which comes in small spray cans. Versions including CS are manufactured for police use.[26] Xylyl bromide, CN and CS are the oldest of these agents. CS is the most widely used. CN has the most recorded toxicity.[3]

Typical manufacturer warnings on tear gas cartridges state "Danger: Do not fire directly at person(s). Severe injury or death may result."[27] Tear gas guns do not have a manual setting to adjust the range of fire. The only way to adjust the projectile's range is to aim towards the ground at the correct angle. Incorrect aim will send the capsules away from the targets, causing risk for non-targets instead.[28]


A variety of protective equipment may be used, including gas masks and respirators. In riot control situations, protesters sometimes use equipment (aside from simple rags or clothing over the mouth) such as swimming goggles and adapted water bottles.[29]

Activists in United States, Czech Republic, Venezuela and Turkey have reported using antacid solutions such as Maalox diluted with water to repel effects of tear gas attacks[30][31][32] with Venezuelan chemist Mónica Kräuter recommending the usage of diluted antacids as well as baking soda.[33] There have also been reports of these antacids being helpful for tear gas,[34] and for capsaicin-induced skin pain.[35]

During the 2019 Hong Kong protests, frontline protesters became adept at extinguishing tear gas: they formed special teams that spring into action as soon as it is fired. These individuals generally wear protective clothing, including heat-proof gloves, or cover their arms and legs with cling film to prevent the painful skin irritation. Canisters are sometimes picked up and lobbed back at police or extinguished straight away with water, or neutralised using objects such as traffic cones. They share information about models of 3M respirator filters which have been found to be most effective against tear gas, and where those models could be purchased. Other volunteers carry saline solutions to rinse the eyes of those affected.[36] Similarly Chilean protesters of Primera Línea have specialized individuals collecting and extinguishing the tear gas grenades. Others act as tear gas medics while yet another group, the so-called shield-bearers protect the protesters from the direct physical impact of the grenades.[37]


A paramedic tending to an opposition protester during the 2014 Venezuelan protests

There is no specific antidote to common tear gases.[3][38] Getting clear of gas and into fresh air is the first line of action.[3] Removing contaminated clothing and avoiding shared use of contaminated towels could help reduce skin reactions.[39] Immediate removal of contact lenses has also been recommended, as they can retain particles.[39][38]

Once a person has been exposed, there are a variety of methods to remove as much chemical as possible and relieve symptoms.[3] The standard first aid for burning solutions in the eye is irrigation (spraying or flushing out) with water.[3][40] There are reports that water may increase pain from CS gas, but the balance of limited evidence currently suggests water or saline are the best options.[38][34][41] Some evidence suggests that Diphoterine, a hypertonic amphoteric salt solution, a first aid product for chemical splashes, may help with ocular burns or chemicals in the eye.[40][42]

Bathing and washing the body vigorously with soap and water can remove particles that adhere to the skin. Clothes, shoes and accessories that come into contact with vapors must be washed well since all untreated particles can remain active for up to a week.[43] Some advocate using fans or hair dryers to evaporate the spray, but this has not been shown to be better than washing out the eyes and it may spread contamination.[38]

Anticholinergics can work like some antihistamines as they reduce lacrymation and decrease salivation, acting as an antisialagogue, and for overall nose discomfort as they are used to treat allergic reactions in the nose (e.g., itching, runny nose, and sneezing).[]

Oral analgesics may help relieve eye pain.[38]

Home remedies

Vinegar, petroleum jelly, milk and lemon juice solutions have also been used by activists.[44][45][46][47] It is unclear how effective these remedies are. In particular, vinegar itself can burn the eyes and prolonged inhalation can also irritate the airways.[48] Though vegetable oil and vinegar have also been reported as helping relieve burning caused by pepper spray,[39] Kräuter suggests the usage of baking soda or toothpaste, stating that they trap the particles emanating from the gas near the airways that are more feasible to inhale.[33] A small trial of baby shampoo for washing out the eyes did not show any benefit.[38]

See also


  1. ^ "Mace" is a brand name for a tear gas spray
  2. ^ E.g. the Geneva Protocol of 1925 prohibited the use of "asphyxiating gas, or any other kind of gas, liquids, substances or similar materials".


  1. ^ Tear gas: an epidemiological and mechanistic reassessment by Jeffrey D. Laskin, Craig Rothenberg, Satyanarayana Achanta, Erik R. Svendsen, and Sven-Eric Jordt
  2. ^ a b c Rothenberg C, Achanta S, Svendsen ER, Jordt SE (August 2016). "Tear gas: an epidemiological and mechanistic reassessment". Annals of the New York Academy of Sciences. 1378 (1): 96-107. Bibcode:2016NYASA1378...96R. doi:10.1111/nyas.13141. PMC 5096012. PMID 27391380.
  3. ^ a b c d e f g h Schep LJ, Slaughter RJ, McBride DI (June 2015). "Riot control agents: the tear gases CN, CS and OC-a medical review". Journal of the Royal Army Medical Corps. 161 (2): 94-9. doi:10.1136/jramc-2013-000165. PMID 24379300.
  4. ^ a b c Smith J, Greaves I (March 2002). "The use of chemical incapacitant sprays: a review" (PDF). The Journal of Trauma. 52 (3): 595-600. doi:10.1097/00005373-200203000-00036. PMID 11901348.
  5. ^ National Research Council (US) Committee on Toxicology (2011). "National Research Council (US) Committee on Acute Exposure Guideline". PMID 24983066. Cite journal requires |journal= (help)
  6. ^ a b Kearney T, Hiatt P, Birdsall E, Smollin C (July-September 2014). "Pepper spray injury severity: ten-year case experience of a poison control system". Prehospital Emergency Care. 18 (3): 381-6. doi:10.3109/10903127.2014.891063. PMID 24669935.
  7. ^ Heinrich U (September 2000). "Possible lethal effects of CS tear gas on Branch Davidians during the FBI raid on the Mount Carmel compound near Waco, Texas" (PDF). Prepared for The Office of Special Counsel John C. Danforth.
  8. ^ a b Hu H, Fine J, Epstein P, Kelsey K, Reynolds P, Walker B (August 1989). "Tear gas--harassing agent or toxic chemical weapon?" (PDF). JAMA. 262 (5): 660-3. doi:10.1001/jama.1989.03430050076030. PMID 2501523. Archived from the original (PDF) on 29 October 2013.
  9. ^ Clarot F, Vaz E, Papin F, Clin B, Vicomte C, Proust B (October 2003). "Lethal head injury due to tear-gas cartridge gunshots". Forensic Science International. 137 (1): 45-51. doi:10.1016/S0379-0738(03)00282-2. PMID 14550613.
  10. ^ Wani ML, Ahangar AG, Lone GN, Singh S, Dar AM, Bhat MA, et al. (March 2011). "Vascular injuries caused by tear gas shells: surgical challenge and outcome". Iranian Journal of Medical Sciences. 36 (1): 14-7. PMC 3559117. PMID 23365472.
  11. ^ Wani AA, Zargar J, Ramzan AU, Malik NK, Qayoom A, Kirmani AR, et al. (2010). "Head injury caused by tear gas cartridge in teenage population". Pediatric Neurosurgery. 46 (1): 25-8. doi:10.1159/000314054. PMID 20453560.
  12. ^ Carron PN, Yersin B (June 2009). "Management of the effects of exposure to tear gas". BMJ. 338: b2283. doi:10.1136/bmj.b2283. PMID 19542106.
  13. ^ Worthington E, Nee PA (May 1999). "CS exposure--clinical effects and management". Journal of Accident & Emergency Medicine. 16 (3): 168-70. doi:10.1136/emj.16.3.168. PMC 1343325. PMID 10353039.
  14. ^ Oksala A, Salminen L (December 1975). "Eye injuries caused by tear-gas hand weapons". Acta Ophthalmologica. 53 (6): 908-13. doi:10.1111/j.1755-3768.1975.tb00410.x. PMID 1108587.
  15. ^ "INDH se querella por homicidio frustrado contra Carabineros en favor de trabajadora que habría perdido visión de ambos ojos". Instituto Nacional de Derechos Humanos (in Spanish). 27 November 2020. Retrieved 2020.
  16. ^ "INDH presenta querella por joven que perdió un ojo por lacrimógena en año nuevo en Plaza Italia". Instituto Nacional de Derechos Humanos (in Spanish). 8 January 2020. Retrieved 2020.
  17. ^ "INDH se querella por lesión a profesor que perdió un ojo en Valparaíso". Instituto Nacional de Derechos Humanos (in Spanish). 4 January 2020. Retrieved 2020.
  18. ^ Bessac BF, Sivula M, von Hehn CA, Caceres AI, Escalera J, Jordt SE (April 2009). "Transient receptor potential ankyrin 1 antagonists block the noxious effects of toxic industrial isocyanates and tear gases". FASEB Journal. 23 (4): 1102-14. doi:10.1096/fj.08-117812. PMC 2660642. PMID 19036859.
  19. ^ Brône B, Peeters PJ, Marrannes R, Mercken M, Nuydens R, Meert T, Gijsen HJ (September 2008). "Tear gasses CN, CR, and CS are potent activators of the human TRPA1 receptor". Toxicology and Applied Pharmacology. 231 (2): 150-6. doi:10.1016/j.taap.2008.04.005. PMID 18501939.
  20. ^ Jones DP (April 1978). "From Military to Civilian Technology: The Introduction of Tear Gas for Civil Riot Control". Technology and Culture. 19 (2): 151-168. doi:10.2307/3103718. JSTOR 3103718.
  21. ^ "Practice Relating to Rule 75. Riot Control Agent". ihl-databases.icrc.org/. IHL Database. Retrieved 2020.
  22. ^ 100 Years of Tear Gas, The Atlantic, August 16, 2014
  23. ^ "Co. G recruits use new gas mask in confidence chamber". tecom.marines.mil. Marine Corps Websites. Retrieved 2019.
  24. ^ "Recruits feel effects of Confidence Chamber". mcrdsd.marines.mil. Marine Corps Websites. Retrieved 2019.
  25. ^ "MoD confirms army CS gas investigation". Politics.co.uk. 13 May 2006. Archived from the original on 9 October 2013. Retrieved 2013.
  26. ^ "Mace pepper spray". Mace (manufacturer). Retrieved 2014.
  27. ^ Smith E (28 January 2011). "Controversial tear gas canisters made in the USA". Africa. CNN.
  28. ^ Turkish Doctors' Association, 16 June 2013, TÜRK TAB?PLER? B?RL'NDEN AC?L ÇA?RI !
  29. ^ "Gezi park protesters bring handmade masks to counter police tear-gas rampage". Hürriyet Daily News.
  30. ^ Ferguson D (28 September 2011). "'Maalox'-and-water solution used as anti-tear gas remedy by protesters". Raw Story.
  31. ^ "Medical information from Prague 2000". Archived from the original on 18 October 2014.
  32. ^ Ece Temelkuran (3 June 2013). "Istanbul is burning". Occupy Wall Street.
  33. ^ a b "Prof USB Mónica Kräuter, Cómo reaccionar ante las bombas lacrimógenas". Tururutururu (in Spanish). 26 May 2017. Retrieved 2017.
  34. ^ a b Carron PN, Yersin B (June 2009). "Management of the effects of exposure to tear gas". BMJ. 338: b2283. doi:10.1136/bmj.b2283. PMID 19542106.
  35. ^ Kim-Katz SY, Anderson IB, Kearney TE, MacDougall C, Hudmon KS, Blanc PD (June 2010). "Topical antacid therapy for capsaicin-induced dermal pain: a poison center telephone-directed study". The American Journal of Emergency Medicine. 28 (5): 596-602. doi:10.1016/j.ajem.2009.02.007. PMID 20579556.
  36. ^ "Hong Kongers get creative with traffic cones and kitchenware to fight tear gas". Japan Times. 9 August 2019. Archived from the original on 7 November 2019. Retrieved 2019.
  37. ^ Claude, Magdalena (6 January 2020). "Retrato de un clan de la Primera Línea". CIPER Chile (in Spanish). Retrieved 2020.
  38. ^ a b c d e f Kim YJ, Payal AR, Daly MK (2016). "Effects of tear gases on the eye". Survey of Ophthalmology. 61 (4): 434-42. doi:10.1016/j.survophthal.2016.01.002. PMID 26808721.
  39. ^ a b c Yeung MF, Tang WY (December 2015). "Clinicopathological effects of pepper (oleoresin capsicum) spray". Hong Kong Medical Journal. 21 (6): 542-52. doi:10.12809/hkmj154691. PMID 26554271.
  40. ^ a b Chau JP, Lee DT, Lo SH (August 2012). "A systematic review of methods of eye irrigation for adults and children with ocular chemical burns". Worldviews on Evidence-Based Nursing. 9 (3): 129-38. doi:10.1111/j.1741-6787.2011.00220.x. PMID 21649853.
  41. ^ Brvar M (February 2016). "Chlorobenzylidene malononitrile tear gas exposure: Rinsing with amphoteric, hypertonic, and chelating solution". Human & Experimental Toxicology. 35 (2): 213-8. doi:10.1177/0960327115578866. PMID 25805600.
  42. ^ Viala B, Blomet J, Mathieu L, Hall AH (July 2005). "Prevention of CS 'tear gas' eye and skin effects and active decontamination with Diphoterine: preliminary studies in 5 French Gendarmes". The Journal of Emergency Medicine. 29 (1): 5-8. doi:10.1016/j.jemermed.2005.01.002. PMID 15961000.
  43. ^ "Who, What, Why: How dangerous is tear gas?". BBC. 25 November 2011. Retrieved 2017.
  44. ^ Agence France-Press. "Tear gas and lemon juice in the battle for Taksim Square". NDTV. Retrieved 2013.
  45. ^ Doyle M (24 June 2013). "Turks in Pittsburgh concerned for their nation". Pittsburgh Post-Gazette.
  46. ^ Arango T (15 June 2013). "Police Storm Park in Istanbul, Setting Off a Night of Chaos". The New York Times.
  47. ^ Hughes G (25 June 2013). "Denbigh man tear gassed". The Free Press.
  48. ^ "Vinegar EHS". Toxics Use Reduction Institute, UMAss Lowell. Retrieved 2013.

Further reading

  • Feigenbaum A (2016). Tear Gas: From the Battlefields of WWI to the Streets of Today. New York and London: Verso. ISBN 978-1-784-78026-5.
  • Brône B, Peeters PJ, Marrannes R, Mercken M, Nuydens R, Meert T, Gijsen HJ (September 2008). "Tear gasses CN, CR, and CS are potent activators of the human TRPA1 receptor". Toxicology and Applied Pharmacology. 231 (2): 150-6. doi:10.1016/j.taap.2008.04.005. PMID 18501939.

External links

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