Sick people STINK: Research suggests that illness changes the way you smell

Our sense of smell is a portal of understanding into the microbial world we cannot see. The odors of volatile chemicals are an insight into the world of plants, fungi, insects, and bacteria. Understanding these odor signals can help us differentiate what is unhealthy and what is good for us. Different smells can help us identify which species of bacteria are most dominant, whether there are dangerous microbes present, or if healthy microbes are colonizing the terrain.

There is a difference between the smell of a wound that is healing and the stench of decaying flesh. In each, a different set of bacteria cells are colonizing. There is a difference between the body odor of someone who regularly eats vegetables compared to someone who primarily eats meat and refined sugar. The bacteria on the skin metabolize fatty acids from a person’s sweat, producing different odors, especially in the armpits and genital region. (Related: Babies smell their mother’s fear to learn what to be afraid of.)

Personal odors are a source of information about one’s health and they impact others’ smell

Research from the Monell Center underlines the significance of personal odors as a source of information about a person’s health. Not only does illness change the way you smell, but when sick animals share an environment with healthy ones, the healthy animals begin to take on the odors of the sick animals. This research indicates the contagious nature of unhealthy microbes. Sick people stink and spread this stink to the people around them. This stink is an indication of bacteria ecosystems and is an odor of warning to people nearby.

The research, published in Scientific Reports, suggests that nasty odors associated with sickness are warning signals to others nearby that there is an unhealthy microbial terrain that can impact biological changes to surrounding people. The researchers injected an infectious bacterial toxin into mice. As their immune system activated, the smell of the mice began to change. After these sick mice were placed in the same cages as healthy animals, the bioassays of the healthy mice began to take on the stink from the sick mice. The findings were replicated using a statistical predictive model that identified urinary odor compounds via analytical chemistry. The behavioral bioassay findings showed that stinky odor compounds from sick mice changed the odors of healthy mice to mimic the stink of the sick animals.

The importance of microbial terrains in disease prevention

The research sheds a light on how disease spreads and the important role microbial terrains play in warding off sickness. The stinky odor of a sick person triggers an innate response in healthy people, as they move away to avoid unhealthy microbes. If you dislike someone who stinks, you are experiencing a survival mechanism that helps you minimize the risk of impending infection. The stinky odor is also a warning signal to the person who is sick, alerting them to make changes to re-establish a healthy body. Body odors change when the immune system is activated, signaling to a person’s olfactory nerves that there is the possibility of an impending infection. Understanding one’s own body odors is important for prevention of disease. What does your body need when your scent begins to change? The body may be signaling it needs more probiotics for assimilation of nutrients and a more speedy response to infectious pathogens. The body may be calling out for more plant-based antioxidants and phytonutrients to help restore its disease-fighting capabilities.

Monell behavioral biologist Gary Beauchamp, Ph.D. says there is a “remarkable transfer of information via olfaction that specifically alters physiology.” By understanding these smells, humans can gain insight into how disease transfers from one person to the next and how to best prepare microbial terrains for better disease prevention.

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