The U.S. Agency for Toxic Substances & Disease Registry, ATSDR, states that mild cases of ammonia inhalation result in coughing and nose, eye and throat irritation. Severe exposures to gaseous ammonia can result in chemical burns to the nasal passages, eyes and respiratory tract.
According to the ATSDR, prolonged contact with ammonia triggers swelling and narrowing of the throat and the lung's airways. Severe swelling can obstruct the lungs making breathing difficult or impossible. Prolonged contact with high concentrations of ammonia also puts a person at risk of temporary or permanent blindness, lung disease and even death.
The ATSDR states that ammonia's harmful effects are the result of its reaction with moisture. When ammonia contacts the mucus membranes in bodily tissues, such as the eyes and throat, it forms a caustic alkaline solution known as ammonium hydrate. This results in chemical burns to the exposed tissues. The pungent smell of ammonia serves as a clear warning to its presence and occurs at concentrations as low as 5 parts per million, which do not pose a health risk. When working around ammonia-based chemicals, such as household cleaners and fertilizers, a person needs to provide ample ventilation to the area, wear protective clothing and leave the affected area if irritation occurs.