Does it sound crazy that you could “catch” pain in a whiff? Well, you may think I’m “cheesy” for even suggesting it, but the connection came right out of a 2016 article in Science Advances.
In a recent study, “Social transfer of pain in mice,” researchers examined the connection between the perception and experience of pain by mice who were “bystanders” to their housemates’ unpleasant conditions of either persistent inflammation or withdrawal from opioids and alcohol. These scientists did indeed get some of the unfortunate selected critters drunk, addicted, and inflamed and noted the response of their fellow cage companions. (I know, it’s horrible!) They also compared a control condition of mice in separate housing to determine an effect of the intervention itself based on mechanical, thermal, and chemical tests.
Interestingly, the findings demonstrated that the rodents who witnessed their furry friends abnormally high states of pain (hyperalgesia) literally “felt their pain.” As with humans, gender seemed to influence responsiveness, with female rodents generally experiencing greater hypersensitivity. The authors found no connection between visual cues and were not able to prove that stress patterns served as causative factors in this “contagious pain response.”
Rather, the empathetic little fellows’ discomfort was mediated by their noses, AKA olfactory cues! Below is an excerpt from the study’s discussion reporting on the specifics of how smell alone influenced the perception of the animals’ pain:
Our findings reveal that exposure to olfactory cues from primary mice experiencing hyperalgesia can trigger hyperalgesia in mice housed and tested in the same environment (bystanders). These bystander mice demonstrate hypersensitivity that does not require injury or noxious stimulation but that is acquired following exposure to olfactory cues in the social environment. Under the current experimental conditions, this phenomenon reliably occurs during multiple pain states, including local inflammation (CFA) and hypersensitivity during drug withdrawal (morphine- or alcohol-induced). This socially transferred hyperalgesia can be measured by standard mechanical, thermal, and chemical pain tests. Furthermore, we demonstrate that the phenomenon of social transfer can occur via an olfactory mechanism because 24 hours of exposure to bedding from hyperalgesic mice was sufficient to induce hyperalgesia in otherwise naïve mice. However, we cannot eliminate the possibility that other sensory modalities could also play a role. By examining the social communication of pain, these findings highlight the importance of environmental and social variables in conducting and interpreting preclinical pain research. At the same time, they help elucidate the relationship between alcohol abuse and pain. (1)
These results supported that rodents could play a role for understanding the complex social and environmental interactions related to pain and alcoholism. The authors also noted that their study had implications for past understandings of results obtained in previous mouse and rat studies. Specifically, olfactory stimuli could have skewed interpretations of the experiment, especially when odorant effects weren’t even known or considered!
A write-up in Stat; however, reported that some researchers were skeptical of these findings in the rodents translating to humans. Still, others were curious for more information:
The implications don’t just apply to lab mice. If the same is true of humans — a big if — then pain doctors may want to talk not just to their patients, but to their families and roommates, too. “If you are living with a chronic pain patient, what’s the impact on you?” asked Martin.
Robert Kerns, a Yale pain researcher and a former national director of pain management for the Department of Veterans Affairs, warned that mouse studies cannot necessarily be applied to people.
To him, though, this study underlines the idea, widely accepted among specialists, that a patient’s emotional and social context contribute to pain. “It’s problematic to say that somebody’s pain is not real, or it’s psychological, just because we haven’t developed the technology to uncover or understand the biological contributors,” he said. “It’s critically important for the clinician … to show respect for their experience of pain, and to acknowledge the limits of biomedical science.” (2)
More Full-Body Effects of Smell
If you’ve been reading my blogs for awhile, you may remember I’ve written on the topic of smell and the effects on our body in several contexts:
- The smell of emotions which discussed a previous critter study in which baby rodents experienced fear through an olfactory association (the scent of peppermint) on their frightened, conditioned mothers.
- The power of smells to effect emotions via psychology, physiology, and biochemistry.
- How smell is being used as an indicator of longevity, Alzheimer’s disease, and Parkinson’s disease
- The sense of smell is intricately linked to emotion and social interaction from previous associations and from odorant biochemical properties. Smell, therefore, could both positively and negatively impact social cues from the emitter, as well as effecting pheromones.
- There is an interaction between an association of smell to environmental cues and memory retrieval, emotional reactions, and physiological response. (3) (4) (5) For example, most people have experienced how the same smell may evoke different responses (psychologically and physiologically) in different friends based on the context and their association with the smell. (6) Furthermore, cultural norms also play a part in response to an odor. (7)
- Smell is beyond the nose. For example, a 2014 article noted that odor receptors where found throughout the body, not just the nose. They have been found in the skin (think topical application of essential oils), testes, prostate, muscles, lungs, and more are being found as time progresses. In fact, Science Daily just reported this month on the finding of two new odor receptors in the lungs!
Sniffing Out Pain
Recently, I wrote a two-part article that was published in the Townsend Letter exploring the complex mechanisms of how smell is linked to pain reception. I also discuss the role of essential oils in modulating discomfort. You can find Part I here. Part II will be released in December 2016!
So, my dear friends, do you see why I’m so intrigued with essential oils and the sense of smell in general? As a naturopathic doctor, we were always taught to connect all the body’s systems together and to treat the whole person. Functional medicine regards this connection in the matrix. I say, let’s not forget to look right under our nose for holistic healing!
Do you see why grandma bakes those cookies and why they are comforting now?
Practical Application Alert:
Think of a smell that brings you comfort and is healthy. (For oilers, this will be easy!) It can be an essential oil, a homemade meal, or the scent of a specific flower.
Try to incorporate that smell into your day and see how your day goes. Report and share below. Have a sensational week!
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This material is for information purposes only and is not intended to diagnose, treat, or prescribe for any illness. You should check with your doctor regarding implementing any new strategies into your wellness regime. These statements have not been evaluated by the FDA.