According to Elise Hancock of Johns Hopkins Magazine, people lose their sense of taste when they have a cold, because most of what makes up taste is in fact smell that is triggered by odor molecules from foods and drinks. When eating or drinking, humans smell some molecules in the air as the food approaches. Other molecules vaporize during the chewing process and then rise into the nasal passages.
Go Ask Alice of Columbia Health states that the olfactory receptor cells located at the top of the nasal cavity are responsible for measuring the odors that provide humans with the variety of flavors associated with foods. This means that if the nasal passage is blocked by mucus, the odors from food cannot reach the olfactory cells. A runny nose due to cold can prevent air from reaching smell receptors in the nose. This causes most foods to taste almost identical.
Tastebuds are only capable of detecting sweet, sour, salty and bitter tastes. Donald Leopold, an otolaryngologist at Hopkins’ Bayview Medical Center, states that 80 percent of what people eat is likely tasted through the sense of smell. People could possibly mistake a bite of onion for an apple when they have a cold.
According to Medline Plus, a service of the U.S. National Library of Medicine, the sense of smell enhances a person’s ability to taste. Thus, losing the sense of smell leads to changes in taste. Many can still tell between sour, bitter, sweet and salty tastes, but most cannot tell between other flavors.