[4] Nitrous oxide has significant medical uses, especially in surgery and dentistry, for its anaesthetic and pain-reducing effects,[5] and it is on the World Health Organization's List of Essential Medicines.

[6] Its colloquial name, "laughing gas", coined by Humphry Davy, describes the euphoric effects upon inhaling it, which cause it to be used as a recreational drug inducing a brief "high".

[19] The first important use of nitrous oxide was made possible by Thomas Beddoes and James Watt, who worked together to publish the book Considerations on the Medical Use and on the Production of Factitious Airs (1794).

With this new equipment being engineered and produced by 1794, the way was paved for clinical trials,[clarification needed] which began in 1798 when Thomas Beddoes established the "Pneumatic Institution for Relieving Diseases by Medical Airs" in Hotwells (Bristol).

The use of nitrous oxide as a recreational drug at "laughing gas parties", primarily arranged for the British upper class, became an immediate success beginning in 1799.

While the effects of the gas generally make the user appear stuporous, dreamy and sedated, some people also "get the giggles" in a state of euphoria, and frequently erupt in laughter.

[24] The first time nitrous oxide was used as an anaesthetic drug in the treatment of a patient was when dentist Horace Wells, with assistance by Gardner Quincy Colton and John Mankey Riggs, demonstrated insensitivity to pain from a dental extraction on 11 December 1844.

The reason for this was most likely that Wells, in January 1845 at his first public demonstration to the medical faculty in Boston, had been partly unsuccessful, leaving his colleagues doubtful regarding its efficacy and safety.

[20] When Joseph Thomas Clover invented the "gas-ether inhaler" in 1876, however, it became a common practice at hospitals to initiate all anaesthetic treatments with a mild flow of nitrous oxide, and then gradually increase the anaesthesia with the stronger ether or chloroform.

Clover's gas-ether inhaler was designed to supply the patient with nitrous oxide and ether at the same time, with the exact mixture being controlled by the operator of the device.

Colton's popularisation of nitrous oxide led to its adoption by a number of less than reputable quacksalvers, who touted it as a cure for consumption, scrofula, catarrh and other diseases of the blood, throat and lungs.

Nitrous oxide treatment was administered and licensed as a patent medicine by the likes of C. L. Blood and Jerome Harris in Boston and Charles E. Barney of Chicago.

[34] While N2O affects several ion channels, its anaesthetic, hallucinogenic and euphoriant effects are likely caused mainly via inhibition of NMDA receptor-mediated currents.

The effects of inhaling sub-anaesthetic doses of nitrous oxide may vary unpredictably with settings and individual differences;[36][37] however, Jay (2008)[38] suggests that it reliably induces the following states and sensations: A minority of users also experience uncontrolled vocalisations and muscular spasms.

Originally meant to provide the Luftwaffe standard aircraft with superior high-altitude performance, technological considerations limited its use to extremely high altitudes.

It sometimes could be found on Luftwaffe aircraft also fitted with another engine-boost system, MW 50, a form of water injection for aviation engines that used methanol for its boost capabilities.

It is important with nitrous oxide augmentation of petrol engines to maintain proper and evenly spread operating temperatures and fuel levels to prevent pre-ignition (also called detonation or spark knock).

[28] Today, the gas is administered in hospitals by means of an automated relative analgesia machine, with an anaesthetic vaporiser and a medical ventilator, that delivers a precisely dosed and breath-actuated flow of nitrous oxide mixed with oxygen in a 2:1 ratio.

[91][92][93] Dentists use a simpler machine which only delivers an N2O/O2 mixture for the patient to inhale while conscious but must still be a recognised purpose designed dedicated relative analgesic flowmeter with a minimum 30% of oxygen at all times and a maximum upper limit of 70% nitrous oxide.

[94] Inhalation of nitrous oxide is used frequently to relieve pain associated with childbirth, trauma, oral surgery and acute coronary syndrome (including heart attacks).

[96] In Canada and the UK, Entonox and Nitronox are used commonly by ambulance crews (including unregistered practitioners) as rapid and highly effective analgesic gas.

[97] Recreational inhalation of nitrous oxide, to induce euphoria and slight hallucinations, began with the British upper class in 1799 in gatherings known as "laughing gas parties".

[citation needed] The National Institute for Occupational Safety and Health recommends that workers' exposure to nitrous oxide should be controlled during the administration of anaesthetic gas in medical, dental and veterinary operators.

[107] Exposure to nitrous oxide causes short-term impairment of cognition, audiovisual acuity, and manual dexterity, as well as spatial and temporal disorientation,[108] putting the user at risk of accidental injury.

[38] Nitrous oxide is neurotoxic, and medium or long-term habitual consumption of significant quantities can cause neurological harm with the potential for permanent damage if left untreated.

Inhalation of pure nitrous oxide causes oxygen deprivation, resulting in low blood pressure, fainting, and even heart attacks.

[129] On the other hand, since about 40% of the N2O entering the atmosphere is the result of human activity,[68] control of nitrous oxide is part of efforts to curb greenhouse gas emissions.

[130] Most human caused nitrous oxide released into the atmosphere is a greenhouse gas emission from agriculture, when farmers add nitrogen-based fertilizers onto the fields, and through the breakdown of animal manure.

In August 2015, the Council of the London Borough of Lambeth (UK) banned the use of the drug for recreational purposes, making offenders liable to an on-the-spot fine of up to £1,000.

[137] In September 2023, the UK Government announced that nitrous oxide would be made illegal by the end of the year, with possession potentially carrying up to a two-year prison sentence or an unlimited fine.