Here's What Actually Causes The 'Hospital Smell' Phenomenon

Yes, hospitals have a very distinct smell, and it's not exactly pleasant. Step into any modern hospital, and the odor that meets your nose is usually distressingly reminiscent of any other hospital. This isn't a coincidence. The "hospital smell" comes from a cocktail of disinfectants, which are used to sterilize non-living surfaces, and antiseptics, which are used to sterilize living tissue. (Interestingly, some compounds can be used as both, such as isopropyl alcohol and chloroxylenol, commonly known as Dettol.) In any case, hospitals use massive quantities of disinfectants and antiseptics in their fight against infection. It's a noble struggle with an unfortunate, stinky side effect.

Hospitals use disinfectants to clean walls, floors, furniture, medical instruments, and many other non-living surfaces throughout the facility. Antiseptics are used to sterilize wounds, and they can contribute to the hospital smell as well. While less potent and not used in the same quantities as disinfectants, antiseptics like isopropyl alcohol, hydrogen peroxide, povidone-iodine, and benzalkonium chloride are all volatile compounds that can add to the stinkiness of a hospital.

The idea that hospitals use chemicals to cover up other smells is mostly a myth, however. Bad odors from infected wounds, bodily fluids, and organic gases are certainly present in a hospital, and staff members sometimes put essential oils or Vicks Vaporub in their masks to help deal with the smells. But for visitors, such "natural" smells are usually confined to individual rooms, and the building's HVAC systems remove them from common areas like hallways. The smell of sterilizing chemicals, however, is omnipresent. Common disinfectants include chlorine, hydrogen peroxide, peracetic acid, and ammonia; that last one, ammonia, provides physical properties to household cleaners like Windex, which is why some people might associate the smell of glass-cleaning sprays with the "hospital smell." In general, such disinfectants release the acrid-smelling vapors that are famous for permeating a hospital floor.

When it comes to smells, chemistry doesn't tell the whole story, though. For example, the "old people smell" is easily explained by science, but the association of a distinct odor with the elderly is based on our experiences, as well. Indeed, there's a psychological component involved in all five of our senses, and smell is the sense most closely tied to memory. It's the reason a specific smell can spark a specific memory, such as fallen leaves and the start of the school year. And because hospitals are associated with distressing experiences of illness and injury, the smell of disinfectants is all the more powerful and distinct.

A 2000 research study from Austria demonstrated this association between the smell of a medical facility and the anxiety of the experience. In this case, the team introduced a pleasant orange fragrance to a dental waiting room to mask the smell of disinfectants, and patients were calmer and maintained a more positive mood. This is also why many hospitals place plants and flowers in waiting rooms, and some facilities even offer lavender aromatherapy to reduce stress and anxiety for staff and visitors. 

Interestingly, hospitals didn't always smell like disinfectants, though smell has actually been associated with the medical field for a long time. Before the 19th century, many medical experts relied on the miasma theory of disease, which posited that bad odors caused disease. This mistaken belief did often led to positive outcomes for patients, albeit indirectly. Hospital rooms were aired out and waste was disposed of, leading to greater sanitary conditions. Fittingly, in the 1870s, miasma theory was replaced by the germ theory of disease, and medical professionals realized the importance of disinfectants and antiseptics. Today, hospitals smell like these chemicals, but it's the price we pay in the fight against infection.