Discarded laughing gas capsules in a street in Detroit, Michigan, USA. Laughing gas, or nitrous oxide, is a gas used recreationally since the late eighteenth century. It produces euphoria, relaxation and hallucinations. It is used in medicine for anaesthesia and pain relief. The capsules seen here are designed for the catering trade to charge whipped cream dispensers, but they are commonly used at clubs, festivals and parties to fill balloons. The gas is then inhaled from a balloon to give a brief 'legal high'. Repeated inhalation may cause oxygen deprivation.