Smelling salts, also known asammonia inhalants,spirit of hartshorn, orsal volatile, arechemical compounds used as stimulants to restore consciousness after fainting.[1]
The usual active compound isammonium carbonate—a colorless-to-white,crystallinesolid ((NH4)2CO3).[1] Because most modern solutions are mixed with water, they should properly be called "aromatic spirits of ammonia".[1] Modern solutions may also contain other products to perfume or act in conjunction with theammonia, such aslavender oil oreucalyptus oil.[2]
Historically, smelling salts have been used on people feelingfaint,[3][4][5] or who have fainted. They are usually administered by others but may be self-administered.
Smelling salts are often used on athletes who have been dazed or knocked unconscious to restore consciousness and mental alertness.[1] Smelling salts are now banned in most boxing competitions because of the concern that their effect could mask a more serious injury.[6]
They are also used as a form of stimulant in athletic competitions (such aspowerlifting,strong man,rugby andice hockey) to "wake up" competitors to perform better.[1][7] In 2005,Michael Strahan estimated that 70–80% ofNational Football League players were using smelling salts as stimulants.[8]
Smelling salts have been used sinceRoman times and are mentioned in the writings ofPliny asHammoniacus sal.[1] Evidence exists of use in the 13th century byalchemists assal ammoniac.[1] In the 14th-century "The Canon's Yeoman's Tale", one ofChaucer'sThe Canterbury Tales, an alchemist purports to usesal armonyak.[9] In the 17th century, the distillation of anammonia solution from shavings ofharts' (deer) horns and hooves led to the alternative name for smelling salts as spirit or salt ofhartshorn.[1]
They were widely used inVictorian Britain to revive fainting women, and in some areas, constables would carry a container of them for that purpose.[10] 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.[11][12] Thesal volatile appears several times inDickens' novelNicholas Nickleby.
The use of smelling salts was widely recommended during theSecond World War, with all workplaces advised by theBritish Red Cross andSt. John Ambulance to keep smelling salts in theirfirst aid boxes.[13]
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Solidammonium carbonate andammonium bicarbonate salts partly dissociate to formNH
3,CO
2 andH
2O vapour as follows:
The smelling salts release ammonia (NH
3) gas, which triggers aninhalation reflex. It causes the muscles that control breathing to work faster by irritating themucous membranes of thenose andlungs.[7]
Fainting can be caused by excessiveparasympathetic andvagal activity that slows theheart and decreasesperfusion of thebrain.[14] The sympathetic irritant effect is exploited to counteract these vagal parasympathetic effects and thereby reverse the faint.[15]
Exposure to ammonia gas in large concentrations for prolonged periods is toxic and can be fatal.[1][5] If a high concentration of ammonia is inhaled too close to the nostril, it might burn the nasal or oral mucosa. The suggested distance is 10–15 centimetres (4–6 in).[1]
The use of ammonia smelling salts to revive people injured during sport is not recommended because it may inhibit or delay a proper and thorough neurological assessment by a healthcare professional,[1] such as afterconcussions when hospitalization may be advisable, and some governing bodies recommend specifically against it.[16] The irritant nature of smelling salts means that they can exacerbate any pre-existingcervical spine injury by causing reflex withdrawal away from them, although this has been found to be a result of holding the smelling salts closer to the nose than recommended.[1]