Can you smell a cold on someone? This intriguing question suggests a nuanced answer rather than a simple yes or no.
The Scent of Illness: Fact or Fiction for Colds?
A common cold does not typically produce a distinct, detectable odor that humans can directly perceive. While some studies suggest humans can subtly detect changes in body odor when an immune system is activated, this is not specific enough to identify a common cold by its scent alone. The body’s response to an acute respiratory infection might induce slight olfactory cues, but these are often too subtle for most people to consciously differentiate as a “cold smell.”
What You Might Be Perceiving
When individuals believe they can smell a cold, they are often perceiving secondary effects or associated symptoms rather than the viral infection itself. Congestion or post-nasal drip can alter a person’s breath, leading to a foul odor due to mucus buildup. Nasal discharge or used tissues may also carry a scent from bacteria and mucus. A general shift in body odor can occur due to fever, increased sweating, or altered metabolic processes as the body fights an infection. Furthermore, the presence of menthol rubs or other cold remedies can contribute to a perceived scent.
The Science of Illness-Related Odors
Illness-related odors center on volatile organic compounds (VOCs). These molecules are released from the human body, reflecting an individual’s metabolic condition. When the body fights an infection, its metabolism changes, leading to the production of different VOCs. These alterations can create an “odor-fingerprint” indicating a shift in physiological status. While these changes are often too subtle for human detection in the case of a common cold, the principle demonstrates why the idea of smelling illness has a scientific basis in other contexts.
Other Illnesses with Distinctive Scents
While a common cold lacks a specific scent, other illnesses produce distinct and recognizable odors. Diabetic ketoacidosis, a serious complication of diabetes, can cause a sweet, fruity, or acetone-like smell on the breath due to high levels of ketones. Severe liver disease can lead to “fetor hepaticus,” described as a musty, sweet, or rotten-egg-like odor on the breath. Typhoid fever produces a smell similar to freshly baked bread from the body. These examples highlight how metabolic changes in diseases release specific volatile compounds, resulting in characteristic scents.