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A Brief History of Smelling Salts

  • Published26 Aug 2019
  • Author Michael W. Richardson
  • Source BrainFacts/SfN
Unconscious Patient (Allegory of Smell). One of five oil-on-board paintings in the series The Senses by Rembrandt.
Rembrandt [Public domain]

Smelling salts are a centuries-old folk remedy for fainting. Going back to the 13th century at least, ammonia — the active ingredient in smelling salts — has been a key component of the doctor’s medicine bag. Recently, physicians largely moved away from smelling salts in favor of simpler techniques to prevent or reverse fainting. 

But as the medical field shied away from it, this old substance found new devotees in professional sports. Boxers, football players, and other athletes often turn to the little packets of ammonia, which they believe increase alertness and get them back into the match quickly, even after a big hit. But is this belief justified by science? We asked neurologist Erin Manning from the Hospital for Special Surgery for the facts.

First off, what causes fainting?

Fainting can have several causes, but the root of it is a lack of blood flow — and thus oxygen — to the brain. Breathing issues or low blood pressure are two of the most common causes of fainting. If a person briefly loses consciousness, they’ll typically fall to the ground. That fall is often enough a remedy to the problem — if they are laying down, the heart doesn’t have to work as hard to get blood to the brain, and they’ll be able to recover quite quickly. Sometimes fainting can cause a person to breathe improperly, which would exacerbate the issue. This is where smelling salts are useful.

How do smelling salts help recovery?

Smelling salts are traditionally made of concentrated ammonia in salt form, which makes them easy to store and apply. If you’ve ever cleaned your bathroom with bleach, you know how caustic the fumes can be. When smelling salts are held up to the nose of a person who has fainted, the ammonia fumes irritate the membranes inside the nostrils. This triggers a breathing reflex — the lungs automatically breathe in and out quickly and deeply in order to clear the nasal passages of the stinging ammonia. The deep inhalation helps reset respiratory patterns, sending more oxygen to the brain as breathing comes back to normal.

Smelling salts were commonly used by physicians, but they’re no longer used as regularly by doctors. If a person is prone to fainting because of low blood pressure or a similar medical condition, most doctors advise you simply to lay down and breathe deeply until your blood flow comes back up to normal. It almost always works, and it’s preferable to inhaling any substance, even if we think the substance is mostly harmless.

The use of smelling salts are trending in many sports, including football, boxing, and hockey. There’s very little fainting on the field, so why are they so common?

There’s this idea that smelling salts cause alertness. For example, boxers may use them after a particularly hard round to help them recover. But there’s very little evidence that this actually helps. There is not much deep scientific research into how smelling salts work, because they’re no longer really used medically. But from what we can tell, all it does is cause the breathing reflex. Increased breathing may help with alertness, but if you’re awake, you can breathe deeply on your own. In the case of a concussion, smelling salts would similarly be ineffective, because concussions are caused by a brain injury, not by oxygen deprivation. So, their use in sports is not backed up by the science.

Are there any dangers to using smelling salts?

The use of smelling salts doesn’t seem to cause any short-term or long-term effects. It would be possible to burn the membranes of the nostrils through overuse, but one would have to be using it often and in heavy doses. 

There is a danger if a person suffered a head injury, either through a concussion that knocked them unconscious, or if they fell on their head after fainting. Because the ammonia is an irritant, it can cause some unconscious people to reflexively jerk their head away or turn their neck. Just as the lungs try to clear the nasal passage, your body instinctively wants to move away from the source of the pain in your nose, like if you put your hand on a hot stove. And in the case of a concussion, it’s very important to keep the head stable or you can risk further injuring the brain. 

It can also make a person who suffered a head injury harder to evaluate. Breathing rate is one of the ways that doctors will judge the severity of a concussion, so applying smelling salts can throw off their assessment, and make it more difficult to treat in the short term.

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