Ammonia inhalants, commonly known as smelling salts, are products designed to release ammonia gas when crushed. These inhalants typically come in a small capsule or ampule containing a mixture of ammonium carbonate, sometimes with added fragrance and water. The chemical reaction liberates ammonia vapor, which is a powerful irritant.
Physiological Mechanism of Action
The chemical ammonium carbonate reacts readily to release ammonia gas, which is highly irritating to the mucous membranes of the nose and respiratory tract. This gas dissolves rapidly upon contact with the moist tissues of the upper airway, forming the corrosive compound ammonium hydroxide. The resulting alkaline solution creates the sensation of intense stinging and burning.
The irritation is not a consequence of the sense of smell but a direct chemical activation of the trigeminal nerve. This nerve is responsible for detecting pain and temperature in the nasal cavity, eyes, and throat. The painful stimulus triggers a protective, involuntary reflex, including a sudden gasp, increased heart rate, and a rapid rise in blood pressure. This reaction is a generalized stress response, leading to the temporary feeling of alertness or arousal.
Acute Health Hazards and Injuries
The corrosive nature of the ammonium hydroxide poses several immediate health hazards. Direct, close-range inhalation of the gas can cause chemical burns to the sensitive lining of the nasal passages, eyes, and throat. Symptoms begin with severe burning, cough, and chest tightness, and in severe cases, chemical trauma can result in nosebleeds or corneal burns.
A concerning immediate reaction is laryngospasm, the involuntary constriction of the vocal cords. This reflex is a defense mechanism against foreign substances entering the lungs, but it can lead to temporary difficulty breathing or upper airway obstruction. The irritant effect can also trigger bronchospasm, a narrowing of the airways. This is dangerous for people with pre-existing respiratory issues like asthma or emphysema.
Repeated or excessively close inhalation increases the concentration of ammonia delivered, leading to more profound tissue destruction. High concentrations can cause pharyngeal and laryngeal edema, which is swelling that can further compromise the airway. Chronic exposure, even at lower levels, carries the risk of persistent bronchial hyperresponsiveness, a condition that mimics asthma symptoms.
Guidelines for Safe Use and Contraindications
Ammonia inhalants are explicitly contraindicated for people with breathing difficulties, such as those with asthma or emphysema, due to the risk of triggering severe bronchospasm. They should also never be used on an individual with a suspected head or neck injury, which is common in sports. The involuntary movement caused by the irritant stimulus could inadvertently exacerbate a serious spinal cord injury or mask concussion symptoms.
When used to prevent or treat fainting (syncope), instructions advise holding the crushed inhalant away from the face and carefully approaching the nostrils. This practice aims to deliver a stimulating, less concentrated dose of ammonia vapor to limit corrosive effects. A recommended safe distance is typically four to six inches from the nose.
While some inhalants are recognized by the FDA for treating syncope, a new regulatory issue involves products marketed as athletic performance enhancers. The FDA has warned consumers not to use unapproved inhalant products for alertness and energy boosting, noting that their safety or effectiveness has not been demonstrated. Using these for a temporary performance boost also carries a risk of psychological dependency or habituation, leading to overuse and chronic irritation of the upper respiratory tract.