Smelling salts

Historically, smelling salts have been used on people feeling faint, or who have fainted. Others usually administer them, but they may also be self-administered. Smelling salts are often used on athletes who have been dazed or knocked unconscious to restore consciousness and mental alertness. They are also used as a form of stimulant in athletic competitions (such as powerlifting, strong man, rugby, and ice hockey) to "wake up" competitors to perform better. == History ==

Smelling salts have been used since Roman times and are mentioned in the writings of Pliny as Hammoniacus sal. Evidence exists of use in the 13th century by alchemists as sal ammoniac. In the 17th century, the distillation of an ammonia solution from shavings of harts' (deer) horns and hooves led to the alternative name for smelling salts as spirit or salt of hartshorn. At that time, smelling salts were commonly dissolved with perfume in vinegar or alcohol and soaked onto a sponge, which was then carried on the person in a decorative container called a vinaigrette. The sal volatile appears several times in Dickens' novel Nicholas Nickleby. The use of smelling salts was widely recommended during the Second World War, with all workplaces advised by the British Red Cross and St. John Ambulance to keep smelling salts in their first aid boxes. == Physiological action ==

's Unconscious Patient (Allegory of Smell) shows a woman using smelling salts to revive a man who has fainted at the hands of a barber-surgeon. Solid ammonium carbonate and ammonium bicarbonate salts partly dissociate to form , and vapour as follows: The smelling salts release ammonia () gas, which triggers an inhalation reflex. It causes the muscles that control breathing to work faster by irritating the mucous membranes of the nose and lungs. Fainting can be caused by excessive parasympathetic and vagal activity that slows the heart and decreases perfusion of the brain. The sympathetic irritant effect is exploited to counteract these vagal parasympathetic effects and thereby reverse the faint. == Risks ==

Exposure to ammonia gas in large concentrations for prolonged periods is toxic and can be fatal. The irritant nature of smelling salts means that they can exacerbate any pre-existing cervical spine injury by causing reflex withdrawal away from them, although this is a result of holding the smelling salts closer to the nose than recommended. == References ==