Merck Manual

Please confirm that you are not located inside the Russian Federation


Riot-Control Chemical Agents

(Tear Gas)


James M. Madsen

, MD, MPH, U.S. Army Medical Research Institute of Chemical Defense (USAMRICD)

Last full review/revision May 2019| Content last modified May 2019
Click here for the Professional Version
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version

There are many types of chemical-warfare agents that affect different parts of the body. Riot-control agents are chemical compounds that were initially developed for crowd control but that have also been used in military conflicts. The term tear gas is often used, but the term is incorrect because it is not a gas. Instead, riot-control agents are solids that can be dissolved and dispersed as liquids or as aerosols (small particles are released explosively or as smoke). Riot-control agents are intended to incapacitate people, not cause serious injury or death, although deaths have occurred. Military versions of these agents include chloroacetophenone (CN, also marketed as Mace®), chlorobenzylidenemalononitrile (CS), dibenzoxazepine (CR), and diphenylaminoarsine (adamsite, or DM, a so-called vomiting agent). Oleoresin capsicum (OC, pepper spray) is a more recently developed riot-control agent used primarily for law enforcement and personal protection. Note that chemical warfare agents typically have a one- to three-letter military code that is easier to use than their chemical name.


Most riot-control agents cause nearly immediate irritation and pain to the eyes, mucous membranes, and skin. People who inhale the agents develop coughing, sneezing, wheezing, and sometimes shortness of breath.

People typically recover from the effects within a half an hour, but agents left on the skin may cause blisters. Some people develop a permanent lung complication called reactive airways dysfunction syndrome, which causes episodes of shortness of breath and wheezing, similar to that caused by asthma.


  • A doctor's evaluation

  • Sometimes chest x-rays

Doctors base the diagnosis on the person's symptoms and history of exposure. People with shortness of breath may need chest x-rays, but other tests are not needed.


  • Removal from exposure

  • Decontamination of affected areas

At the first sign of exposure or potential exposure, masks are applied when available. People are removed from the affected area when possible.

First responders remove the agent by brushing, washing, or rinsing the affected area. Water may temporarily worsen the pain caused by certain riot-control agents (such as pepper spray) but is still effective. Oils or soapy liquids are probably more effective against pepper spray. Eyes are decontaminated by copious flushing with sterile plain or salt water.

Most effects resulting from riot-control agents are short-lasting, and most people do not need to go to the hospital. Even most people with more severe symptoms need to be observed in a hospital for only a few hours.

The views expressed in this article are those of the author and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

More Information

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Also of Interest


View All
Rotator Cuff Injury
Rotator Cuff Injury
The rotator cuff is located in the shoulder. It comprises muscles and tendons that connect...
3D Models
View All
3D Model