A common cold often leads to a diminished sense of smell and, consequently, taste. Olfaction (smell) and gustation (taste) are deeply intertwined. While true taste involves detecting basic sensations like sweet, sour, salty, bitter, and umami, the rich experience of food flavor relies heavily on our sense of smell.
How Colds Affect Smell
A common cold primarily impacts smell through inflammation and obstruction within the nasal passages. The cold virus triggers an immune response, leading to swelling and increased mucus production in the nose. This inflammation constricts nasal airways, making it difficult for air to flow freely.
Olfactory receptors, specialized cells for detecting odors, are located high in the nasal cavity within a region called the olfactory epithelium. Excessive mucus and swelling create a physical barrier, preventing odor molecules from reaching these receptors. Without direct contact, signals for smell perception cannot be generated and sent to the brain.
Beyond physical blockage, the cold virus can also directly affect olfactory neurons. Viruses cause inflammation around these nerve cells, impairing their ability to transmit signals. This direct impairment contributes to the diminished sense of smell during a cold.
The Connection Between Smell and Taste
What is commonly perceived as “taste” is actually a complex sensory experience known as flavor. True taste is limited to five basic sensations detected by taste buds on the tongue: sweet, sour, salty, bitter, and umami. These taste buds typically remain functional even when a person has a cold.
Flavor combines these basic tastes with the information provided by our sense of smell. When food is chewed, it releases aroma compounds that travel up the back of the throat to the nasal cavity, where they are detected by the olfactory system. This process, known as retronasal olfaction, is responsible for the nuanced flavors we experience.
If the sense of smell is compromised during a cold, the brain receives less information about these aroma compounds. While the tongue can still detect basic tastes, the overall perception of flavor is diminished. Foods may seem bland or unappetizing, leading to the sensation that taste has been lost, even though the taste buds themselves are still working.
Recovery and When Sense Returns
The loss of smell and taste with a common cold is typically temporary. As cold symptoms begin to resolve, inflammation and congestion in the nasal passages decrease. This allows air and odor molecules to again reach the olfactory receptors.
For most people, these senses gradually return within a few days to a week or two after symptoms subside. While it is rare for a common cold to cause permanent loss, the return of smell and taste is generally a positive sign that the body is recovering from the infection.