How do smelling salts work? Why do athletes use them?
Smelling salts have recently undergone a resurgence of interest by athletes as a pre‐game stimulant, and it appears that little is known about them.
There is a surprisingly long history of the use of such agents. The term Hammoniacus sal appears in the writings of Pliny. However, it is not known whether the term is identical to the more modern sal ammoniac, which was known to the alchemists as early as the 13th century. Chaucer also noted the existence of sal ammoniac alongside many other materia medica. This spirit was mainly used by textile dyers in the Middle Ages as fermented urine to alter the color of vegetable dyes.
In the 17th century, an aqueous ammonia solution (also called Aquila coelestis) was obtained from distilling shavings of harts’ horns and hooves. When crystallized, this chemical turned out to be ammonium carbonate and was initially called the salt (or spirit) of hartshorn and later became known as smelling salt when mixed with perfumes. It is also known as “baker’s ammonia” and was a forerunner to the more modern leavening agents such as baking soda and baking powder.
By definition, they are any preparations of ammonium carbonate ((NH4)2CO3H2O) and perfume, sniffed as a restorative or stimulant. Traditionally, they were inhaled as a stimulant to relieve faintness or swooning. Smelling salts may also dilute ammonia dissolved in water and ethanol. Most forms of “smelling salts” available online are this latter mixture, and these mixtures should be more correctly termed “aromatic spirits of ammonia.”
Effects and use
Smelling salts stimulate consciousness because the release of ammonia (NH3) gas that escorts their use upsets the membranes of the nose and lungs and thereby initiates an inhalation reflex. This reflex modifies the breathing pattern, improving respiratory flow rates and conceivably alertness.
More recently, athletes have begun to use smelling salts, believing that their use will keep them more alert. Smelling salts is particularly popular among football and hockey players who think this reflex will counteract the effects of concussion.
Are smelling salts likely to work for sport‐related mild head injuries? It is unlikely that the induced inhalational reflex has a significant therapeutic effect over and above the condition’s natural history. Increasing the respiratory rate alone certainly has no beneficial pathophysiological impact on the nature or underlying cause of concussive injury. Whether the salts increase alertness or improve reaction times, or have other positive cognitive benefits remains to be proven scientifically.
Concerning sporting concussions, the real danger is that reaching for smelling salts is not a substitute for a careful and complete neurological assessment. More severe head injuries may often masquerade in the early stages as minor head injuries, and inexperienced carers may falsely assume that an initial improvement, thought to be due to the beneficial effects of smelling salts, may well mask the development of more sinister complications.