Pepper spray
Pepper spray (also known as OC spray (from "Oleoresin Capsicum"), OC gas, capsicum spray, or oleoresin capsicum) is a lachrymatory agent (a chemical compound that irritates the eyes to cause tears, pain, and even temporary blindness) that is used in riot control, crowd control, and personal self-defense, including defense against dogs and bears. It is a less lethal agent that can be deadly in rare cases. The American Civil Liberties Union documented fourteen fatalities from the use of pepper spray as of 1995. The active ingredient in pepper spray is capsaicin, which is a chemical derived from the fruit of plants in the Capsicum genus, including chilis. Long-term effects of pepper spray have not been effectively researched.
Extraction of oleoresin capsicum from peppers involves finely ground capsicum, then the capsaicin is extracted in an organic solvent such as ethanol. The solvent is then evaporated, and the remaining resin is the oleoresin capsicum. An additive such as propylene glycol is used to suspend the OC in water, and pressurized to make it aerosol in pepper spray. The high performance liquid chromatography (HPLC) method is used to measure the amount of capsaicin within pepper sprays. Scoville Heat Units (SHU) are used to measure the hotness of pepper spray.
A synthetic analogue of capsaicin, pelargonic acid vanillylamide (desmethyldihydrocapsaicin), is used in another version of pepper spray known as PAVA spray which is used in England. Another synthetic counterpart of pepper spray, pelargonic acid morpholide, was developed and is widely used in Russia. Its effectiveness compared to natural pepper spray is unclear and it has caused some injuries.
Pepper spray typically comes in canisters, which are often small enough to be carried or concealed in a pocket or purse. Pepper spray can also be bought concealed in items such as rings. There are also pepper spray projectiles available, which can be fired from a paintball gun. Having been used for years against demonstrators , it is increasingly being used by police in routine interventions.

# Effects
Pepper spray is an inflammatory. It causes immediate closing of the eyes, difficulty breathing, runny nose, and coughing. The duration of its effects depend on the strength of the spray but the average full effect lasts around thirty to forty-five minutes, with diminished effects lasting for hours.
The Journal of Investigative Ophthalmology and Visual Science published a study that concluded that single exposure of the eye to OC is harmless, but repeated exposure can result in long-lasting changes in corneal sensitivity. They found no lasting decrease in visual acuity.
The European Parliament Scientific and Technological Options Assessment (STOA) published in 1998 An Appraisal of Technologies of Political Control with extensive information on pepper spray and tear gas. They write:
For those with asthma, taking other drugs, or subject to restraining techniques which restrict the breathing passages, there is a risk of death. The Los Angeles Times has reported at least 61 deaths associated with police use of pepper spray since 1990 in the USA, and the American Civil Liberties Union (ACLU) documented 27 deaths in custody of people sprayed with pepper spray in California alone, since 1993.
The US Army concluded in a 1993 Aberdeen Proving Ground study that pepper spray could cause "Mutagenic effects, carcinogenic effects, sensitization, cardiovascular and pulmonary toxicity, neurotoxicity, as well as possible human fatalities. There is a risk in using this product on a large and varied population". However, the pepper spray was widely approved in the US despite the reservations of the US military scientists after it passed FBI tests in 1991. As of 1999, it was in use by more than 2000 public safety agencies.
The head of the FBI's Less-Than lethal Weapons Program at the time of the 1991 study, Special Agent Thomas W. W. Ward, was fired by the FBI and was sentenced to 2 months in prison for receiving payments from a peppergas manufacturer while conducting and authoring the FBI study that eventually approved pepper spray for FBI use."Prosecutors said that from December 1989 through 1990, Ward received about $5,000 a month for a total of $57,500, from Luckey Police Products, a Fort Lauderdale, Florida-based company that was a major producer and supplier of pepper spray. The payments were paid through a Florida company owned by Ward's wife.
Like tasers, pepper spray has been associated with positional asphyxiation of individuals in police custody. There is much debate over the actual "cause" of death in these cases. There have been few controlled clinical studies of the human health effects of pepper spray marketed for police use, and those studies are contradictory. Some studies have found no harmful effects beyond the effects described above. 

# Deactivation and first aid
Though there is no way of completely neutralizing pepper spray, its effect can be minimized or stopped. Capsaicin is not soluble in water, and even large volumes of water will not wash it off. Victims should be encouraged to blink vigorously in order to encourage tears, which will help flush the irritant from the eyes. The spray can be washed off the face using soap, shampoo, dish washing detergent, or other detergents. Any cooling like ice, cold water, cold surface, or a fan will provide some relief. Milk has been shown to provide some relief and is frequently recommended for treatment of natural capsaicin exposure (chile peppers, hot sauces, spices).  To avoid rubbing the spray into the skin, thereby prolonging the burning sensation, and in order to not spread the compound to other parts of the body, victims should try to avoid touching affected areas. Application of oils, or oil containing creams can trap the capsaicin to the skin and result in more severe chemical burns and blistering.
North American street medics use a non-toxic eyedrop solution of 1:1 water and aluminum hydroxide (Maalox) which helps neutralize pepper spray and relieve symptoms.
Some "triple-action" pepper sprays also contain "tear gas" (CS gas), which can be neutralized with sodium metabisulfite (Campden tablets, used in homebrewing), though it, too, is not water soluble and could be washed off using the same procedure as for pepper spray, Some sprays also contain a UV "blanketing" dye (little can be done against this, but its effects are not nearly as dramatic).

# Legality
Pepper spray is banned for use in war by Article I.5 of the Chemical Weapons Convention which bans the use of all riot control agents in warfare whether lethal or non-lethal.
In Western Australia, it is legal for a person to carry pepper spray for lawful defense, if that person has, on reasonable grounds, a suspicion or belief that he or she will require the pepper spray to defend himself or herself. However, the person found carrying the pepper spray carries the burden of proving a "reasonable belief or suspicion" rather than the prosecution. In all other states and territories in Australia, pepper spray is considered illegal.
In Belgium it is classified as a prohibited weapon, and it is illegal for anyone other than police officers to carry a capsicum spray.
In Canada all products with a label containing the words pepper spray, mace, etc, or otherwise originally produced for use on humans are classified as a restricted weapon. Only Peace Officers, and individuals/corporations who have special government permits may legally carry or possess pepper spray. Any similar canister with the labels reading "dog spray" and/or "bear spray" may be legally carried by anyone.  The legality of using spray intended for animal deterent on a person would be decided in court on a case-by-case basis.
In Denmark possession of pepper spray is illegal for private citizens, but a trial period is currently in effect, where police officers in most metropolitan areas carry pepper spray as part of their standard equipment. This trial period has been initiated following the shooting (and often killing) of a number of mentally ill citizens who have behaved violently or in a threatening manner, leaving the police force in want of a defensive, non-lethal weapon.
In the Dominican Republic, it is legal to own and purchase pepper spray at any age over the counter, CS spray is regulated and may be used only by military personnel on duty. Owning civilian grade pepper spray is endorsed by authorities as means of defense against stray dogs, also as a means of defense against human assailants as opposed to the use of a firearm.
In Finland it is classified as a device governed by the firearm act and possession of pepper spray requires a license. Licenses are issued for defensive purposes and to individuals working jobs where such a device is needed such as the private security sector.
Government organizations such as defense forces and police are exempt. Concentrations are also limited to 5% active ingredient in OC sprays and 2%/2% in combinations sprays such as CN/OC.
In Germany pepper sprays labelled  for the purpose of defense against animals may be owned and carried  by anyone (even minors). Such sprays are not legally considered as weapons 1 WaffG. Carrying it at (or on the way to and from) demonstrations may still be punished  Sprays that are not labelled "animal-defense spray" or do not bear the test mark of the Materialprufungsanstalt (MPA) (material testing institute) are classified as prohibited weapons. Justified use against humans as self-defense is allowed .
CS sprays bearing a test mark of the MPA may be owned and carried by anyone over the age of 14..
In Hong Kong. pepper spray is classified as "arms" under HK Laws. Chap 238 FIREARMS AND AMMUNITION ORDINANCE. Without a valid license from the Hong Kong Police Force, it is a crime and can result a fine of $100,000 and to imprisonment for 14 years.
In Israel, OC and CS spray cans may be purchased by any member of the public without restriction and carried in public. In the 1980s a firearms license was required for doing so, but since then these sprays have been deregulated.
In Italy OC it is considered a self-defense weapon and it is legal to own it when the active principle is less than 10%. Spray made with CS is illegal.
In Latvia pepper spray is classified as a self-defense weapon, and it is available to anyone over 16. Anyone over 18 can buy gas pistol loaded with pepper or tear gas cartridges for self defense.
In the Netherlands it is classified as a Class II weapon of the Weapons and Munition Act(or Wet Wapens en Munitie, in Dutch), putting it in the same class of regulation as fully automatic fire-arms, explosive devices and other war gasses such as organophosphate nerve gasses. It is a prohibited weapon except for police officers, who carry it as a less than lethal weapon, as an alternative for using their side-arm.
In New Zealand pepper spray is carried by police offers in place of a firearm.
In Norway real pepper spray is only used by the police. The publicly available defense spray often called pepper spray is actually based on isopropyl alcohol.
In Poland pepper spray is not classified as a weapon, so it is available to anyone over 18.
In Russia pepper spray is a fully legal self-defense weapon and can be bought without license by any person over the age of 18 (passport being required for purchase). Its effect on animals is advertised as additional feature, compared with tear gas sprays. Carrying it at demonstrations is prohibited by law.
In South Africa it is not a licensed product and is freely available as an over the counter security product. Generally carried and used by private security officers and armed reaction officers as well as police and members of the public. A pepper spray projectile is also available also without license. Anyone using pepper spray as anything but a defensive weapon can still be charged with a firearms offense.
In Sweden it is classified as an offensive weapon and possession of pepper spray requires a license. However, as of 2006, no such license has been issued.
In Spain approved pepper spray made with 5% CS is available to anyone over 18.
In South Korea Pepper spray containing OC is legal, however gas-gun types need a simple license to own. CS is only available for police and private security firms.
In the United Kingdom, "Any weapon of whatever description designed or adapted for the discharge of any noxious liquid, gas or other thing" is classed as a section 5 firearm (Firearms Act 1968). The same act covers other prohibited weapons such as automatic firearms and rocket launchers, all of which can only be possessed by permission of the Home Secretary. Although legal for police officers, recent debates have arisen whether such a weapon should be legal for civilians as means of defensive purposes only. At present a number of legal alternative dye sprays are sold in the UK which have the effect of temporarily blinding the attacker but do not constitute noxious substances and so do not contravene this act.
Laws on pepper spray in the United States of America differ between states.
- Massachusetts, Massachusetts residents may only purchase defense sprays from licensed Firearms Dealers in that state, and must hold a valid Firearms Identification Card (FIC). 
- Wisconsin, Tear gas is not permissible.  By regulation, OC products with a maximum OC concentration of 10% and weight range of oleoresin of capsicum and inert ingredients of 15-60 grams are authorized.  This is 1/2 oz. and 2 oz. spray. Further, the product cannot be camouflaged, and must have a safety feature designed to prevent accidental discharge.  The units may not have an effective range of over 20 feet and must have an effective range of six feet.  In addition there are certain labeling and packaging requirements: must state cannot sell to anyone under 18 and the phone number of the manufacturer has to be on the label.  The units must also be sold in sealed tamper-proof packages.
- Michigan, pepper spray is legal if it has less than 2% of the active ingredient, this decreases the length of the effects but not the SHU. Sprays containing a mixture of CN/CS are also banned, though tear gas containing only CS is legal. Agents meeting these criteria can be possessed by anyone over the age of 18.
- New York, pepper spray may be legally possessed by any person age 18 or over; however, it must be purchased in person (i.e. cannot be purchased by mail-order or internet sale) either at a pharmacy or from a licensed firearm retailer (NY Penal Law 265.20 14 (a)), and the seller must keep a record of purchases. The use of pepper spray to prevent a public official from performing his/her official duties is a class-E felony;
- In many (but not all) other states, pepper spray can be purchased at various stores and carried legally by anyone over 18.