Its use is sometimes controversial.
What is it?
Pepper spray is a lachrymatory agent. This means that it makes the eyes tearful. Pepper spray is based on an oil known as oleoresin capsicum. Capsaicin, the inflammatory agent in the oil, is the same chemical that makes chilli peppers hot. But in pepper spray, it is present at a much higher concentration.
How does the concentration of capsaicin in pepper spray compare with that of household peppers?
The "hotness" of pepper spray far exceeds that of jalapeno peppers.
The heat of a bell pepper measures 0 on the Scoville Heat Units scale, which is used to measure the "heat" of peppers. A jalapeño pepper scores 2,500 to 5,000 on the same scale.
Pepper spray, however, ranges from 2 million units for commercial self-defense use to 5.3 million Scoville units for police-issue pepper spray.
This same ingredient also forms the basis of bear spray, which reduces attacks during human encounters with bears.
However, the concentration of capsaicin in bear spray is only 1 to 2 percent. Pepper sprays used in law enforcement reportedly have a capsaicin content of between 10 and 30 percent. As a result, its deployment has often been controversial, particularly when used against civilian protestors, such as in the Occupy Wall Street protests of 2011.
Pepper spray is classified as a riot-control agent and is banned for use in war by Article I.5 of the Chemical Weapons Convention.
When a person comes into contact with pepper spray, their eyes will close immediately. They will experience a "bubbling" or "boiling" sensation, followed by temporary blindness and eye pain. The effects last from 30 to 45 minutes, depending on how strong the spray solution is.
Pepper spray can also burn the throat, cause wheezing, dry cough, shortness of breath, gagging, gasping and the inability to breathe or speak.
In rare cases, it can cause cyanosis, a bluish discoloration of the skin that indicates a lack of blood flow and oxygen. Apnea and respiratory arrest are possible.
There are wipes and solutions carried by emergency medical technicians for the purpose of treating the symptoms of pepper spray. If you have been sprayed or have got spray on you accidentally, then the the following steps may help to alleviate the burning symptoms of pepper spray.
Since the spray is oil-based, people who have it on their skin are advised not to touch the affected area. Touching the solution can easily spread it to other areas of the body.
If pepper spray enters the eyes, blinking rapidly may help to flush it out.
Washing with hand soap, shampoo, or dish soap can break up the oil. After that, the area should be rinsed with water. Baby shampoos can be useful for washing spray from the eye area.
People who have been sprayed may instinctively want to douse themselves in water. This can provide some instant relief, but it will not last long. Oil does not mix with water on a molecular level, so - like grease on a dirty plate - washing with water alone will not remove the solution.
Since the 1980s, pepper spray has often been used by the police to subdue people who are behaving violently or in an uncooperative way.
The police sometimes used pepper spray.
When pepper spray is sprayed into the face, the subject becomes temporarily blinded. This makes it easier for police officers to remove suspects from a scene and arrest them.
During the Occupy protests, the use of pepper spray by police came under media scrutiny. Videos showed police officers repeatedly spraying peaceful protestors for prolonged periods, although guidelines state that the spray should be used for no more than one second on any person.
The deployment of pepper spray by law enforcement officers can be controversial for other reasons.
A 2016 study by Harvard University researchers, for instance, found that black Americans are 25 percent more likely than white Americans to be pepper sprayed by police.
Pepper spray is known as a "nonlethal weapon," a weapon that cannot kill.
However, deaths have occurred following the use of pepper spray. People with asthma have a higher chance of complications.
In 2003, a Department of Justice report found that pepper spray directly contributed to the deaths of 2 people out of 63 cases, where suspects held in custody died after pepper spray was used in their arrest.
In the two cases where the cause of death was directly attributed to pepper spray, the two people affected had asthma.
The other causes of death were found to be drug use, disease, positional asphyxia, or a combination.
However, the same report concluded that "Pepper spray inhalation alone does not pose a significant risk for respiratory compromise or asphyxiation, even when combined with positional restraint."