Recreational use of nitrous oxide

Nitrous oxide (N₂O), commonly referred to as laughing gas, along with various street names, is an inert gas which can induce euphoria, dissociation, hallucinogenic states of mind, and relaxation when inhaled. Nitrous oxide has no acute biochemical or cellular toxicity and is not metabolized in humans or other mammals. Rare deaths and injuries associated with use are due to asphyxia or accidents related to alcohol, or vitamin B₁₂ deficiency. Excessive use can lead to long-term and significant neurological and haematological toxicity, such as subacute combined degeneration of spinal cord.

First recorded in the 18th century at upper-class "laughing gas parties", the experience was largely limited to medical students until the late 20th century when laws limiting access to the gas were loosened to supply dentists and hospitals. By the 2010s, nitrous oxide had become more popular as a recreational drug in the Western world and other nations.

Increasing recreational use has become a public health concern internationally due to the potential for long-term neurological damage caused by habitual use. Recreational users are often unaware of the risks. Owing to the chemical's numerous legitimate uses, the sale and possession of nitrous oxide is legal in many countries, although some have criminalised supplying it for recreational purposes.