Is N2O safe?

N2O, or nitrous oxide, is safe when administered as an analgesic by a health care professional. It has few side effects and leaves the body quickly. Recreational use is riskier. Users may accidentally asphyxiate themselves by using nitrous oxide within a closed space or with a bag over the head.

Nitrous oxide was originally synthesized in 1772 by Joseph Priestley. Humphry Davy discovered the pain-relieving property of the gas in 1800, but its use as a dental analgesic did not begin until 1844. Modern dentistry usually uses a mixture of 30 percent nitrous oxide and 70 percent oxygen. Signs of oversedation with nitrous oxide include nausea, sleepiness and flashbacks.