How do smelling salts work?

Some athletes use smelling salts in the hopes that it will improve their performance. Here, Chris Kreider (left) and Alexis Lafreniere (right) of the New York Rangers use smelling salts before a game at Madison Square Garden on Nov. 1, 2022 in New York City. (Image credit: Jared Silber/NHLI via Getty Images)

Smelling salts have been used for centuries to keep people alert. They were once prominent in funeral homes and at blood donation drives. Athletes inhale them from the sidelines in hopes of improving their performance. Rocky famously takes a whiff of a smelling salt to get back in the ring and keep up the fight. But how do these smelling salts work?

Smelling salts contain ammonia, a strong and foul-smelling chemical, said Dr. Anthony Alessi (opens in new tab), a clinical professor of neurology and orthopedics at the University of Connecticut. 

The ammonia gas irritates the membranes in the nose and throughout the respiratory system and causes an inhalation reflex, according to a 2006 study in the British Journal of Sports Medicine (opens in new tab). The inhalation reflex changes breathing patterns, increases oxygen flow and gas exchange, and thereby can increase alertness in some situations, the study authors wrote.

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While ammonia can be toxic if ingested in high amounts, a whiff of these salts is safe. However, it may not always be particularly helpful, Alessi said.

While it was once common to use smelling salts to keep athletes conscious after a concussion, this has fallen out of practice because it can be dangerous, Alessi said. It's a reflex to move away from a noxious smell; if an athlete has a head or neck injury, the abrupt smell could cause them to jerk away and worsen their injury. 

Athletes sometimes still use a whiff of smelling salts in an attempt to improve their performance. While the practice may make them feel more alert and focused, there's no evidence that it actually improves muscle strength, according to a 2014 study in the Journal of Exercise Physiology (opens in new tab)

It's also important to note that if a person faints or their consciousness falters, it's because the brain doesn't have everything it needs. It may lack energy or oxygen, so it reboots, Alessi said. This can happen in all kinds of situations, like when people pass out while watching gory movies or when people with diabetes faint due to low blood sugar. In the past, people have rushed to smelling salts because it feels like they are doing something about the loss of consciousness. 

But in reality, fainting is often a protective mechanism pointing to a larger problem that may need medical attention. So, stopping it with smelling salts isn’t really a solution. The "brain is very resilient," Allessi said, and it's protecting and reviving itself. 

This article is for informational purposes only, and is not meant to offer medical advice.

Donavyn Coffey
Live Science Contributor

Donavyn Coffey is a Kentucky-based health and environment journalist reporting on healthcare, food systems and anything you can CRISPR. Her work has appeared in Scientific American, Wired UK, Popular Science and Youth Today, among others. Donavyn was a Fulbright Fellow to Denmark where she studied  molecular nutrition and food policy.  She holds a bachelor's degree in biotechnology from the University of Kentucky and master's degrees in food technology from Aarhus University and journalism from New York University.