Something to sneeze at: Hunger-induced sneezing?

Posted by Susan Lubejko on September 24, 2020 in Neuroscience, Neuroscience of appetite | 3 Comments

If you’re anything like me and crave the look of a pantry or office supplies organized by color in clear bins, you’ve probably, also like me, already binged Netflix’s Get Organized with the Home Edit, in which organizational gurus Clea and Joanna of The Home Edit Instagram fame edit and contain disorganized kitchens, closets, offices, bedrooms, and classrooms. If you are similarly interested in the peculiarities of the human body, you may have hit the pause button as I did during a particular scene in the very last episode of Get Organized in which Clea exhibits an uncommon response to being hungry – a sneeze. In an explanation typical of their hilarious banter, Clea explains, “When I am extremely hungry, I start sneezing, which no one believes is a real thing.” “I believe it now. We looked it up,” responds Joanna. 

So, is this a real, scientifically documented thing? Having recently researched the phenomenon of sneezing in response to bright light – which I myself experience – that enjoys a fairly broad array of scientific theories in published sources, I felt obligated to expand my search for information on non-traditional triggers for sneezing. Are there documented cases of hunger-induced sneezing? What could be going on in the nervous system to cause it?

Truthfully, the accepted data on this phenomenon is sparse. While scientific publications don’t mention hunger-induced sneezing, a quick Google search reveals a plethora of online forums for people experiencing it. Interestingly, however, other unusual bodily triggers for sneezing do pop up occasionally in scientific publications, and while their causes have not been extensively studied, some theories for their origin have been posed. To better understand what may be causing Clea’s hunger-related sneezing, let’s first look at other documented cases of unusual sneezing triggers and how these might be related in the body.

What can trigger sneezing?

    A typical sneeze is triggered by irritation of the nasal lining. Sneezing releases a blast of air through the nose to try to dislodge whatever is causing this irritation, such as a speck of dust. One of the more commonly studied non-irritation causes for sneezing is exposure to bright light. While the exact mechanisms for this phenomenon remain unknown, photic sneezing, the technical term for this type of sneezing, is probably caused by some sort of confused signals between the nerves that sense and control the eyes and those innervating the nasal lining [1]. 

While hunger-induced sneezing doesn’t appear in the published scientific literature, case studies on very small groups of individuals indicate that sneezing can be similarly caused by stomach fullness after eating [2,3], bladder fullness [4], and even sexual ideation and orgasm [3,5]. Though these bodily processes appear unrelated at first, studying the similarities in how they are controlled by our nervous system may help us unravel the basis for hunger-induced sneezing. 

Stomach fullness, bladder fullness, and sexual function are all controlled by the parasympathetic branch of our autonomic nervous system. The autonomic nervous system is the part of our peripheral nervous system (aka the nerves and nerve cells that are outside of our brain and spinal cord to make contact with the rest of our body) that regulates unconscious bodily functions, like heart rate, respiration, and importantly for the sneezing-related functions listed above, digestion, urination, and sexual function. The parasympathetic branch is known for its “rest and digest” functions, which ramps up things like digestion while decreasing heart rate and respiration. 

The stomach, bladder, and sex organs are all contacted by the vagus nerve, one of the main neural pathways from the brain to sense and control parasympathetic function in the body. It is estimated that 90% of the nerve cell pathways that make up the large vagus nerve send signals from the body and its organs to the brain to signal important sensations, such as hunger and satiety. The other 10% of the nerve cells send signals from the brain to the body to provide control over the organs and muscles. Some examples of important vagal nerve functions are controlling the muscles of the throat for swallowing and the muscles that make up the gastrointestinal tract for digestion [6]. 

So, how might these other bodily functions relate to the nose? One group of researchers studying these aberrant sneezes proposes that their cause is precisely this shared involvement in the parasympathetic nervous system. Gastric fullness, for example, is a trigger for the parasympathetic nervous system to send signals to the stomach to increase the secretion of stomach acid to begin digestion. These researchers hypothesize that this parasympathetic response coordinated to communicate with the stomach leads clusters of neurons in the brainstem to mount an overall parasympathetic response in the body. Following this activation, the separate nerve of the parasympathetic system that contacts the nasal lining is also triggered, leading to the secretion of mucus in the nose [4,5]. This secretion in the nose can be irritating enough to cause a subsequent sneeze. This explanation has also been used to explain light-induced sneezing. Although the vagus nerve isn’t involved, other nerves in the face that are part of the parasympathetic nervous system may also be involved in this parasympathetic overdrive that can cause nasal secretions in response to bright light [1].

How could hunger trigger sneezing?

    Hunger is thought to be caused by a variety of chemical signals coming from the body that are interpreted by specific areas of the brain. While it’s not completely understood yet, it appears that nerve cells in the gastrointestinal tract detect two major things: changes in blood sugar levels and the chemical ghrelin. Ghrelin is released by cells in the stomach during fasting periods and has been shown to affect the activity of the all-important and familiar vagus nerve through its connections in the stomach [7]. Because the vagus nerve is involved in the perception and control of hunger, it isn’t a stretch to imagine that hunger may, similarly to stomach fullness, cause a coordinated parasympathetic response that can induce a sneeze.

Additionally, an internet search of non-traditional sneezing triggers reveals that certain people experience nausea that is relieved by sneezing. While this phenomenon also requires further study and is not reflected in accepted scientific publications, it is thought that the nausea could be caused by stomach acid or inflammation of the lining of the stomach, both of which can irritate the vagus nerve. As we have already seen, an activation of the vagus nerve can induce sneezing in some people through parasympathetic mechanisms. Interestingly, we have no idea why the sneeze seems to relieve the nausea in patients that experience this, further underscoring the complexities of how the nervous system coordinates control of different bodily functions. Nonetheless, if you ever experience heartburn when hungry, you may be familiar with the irritating effects of stomach acid on an empty stomach. Perhaps this irritation is another cause for sneezing induced by being hungry.

Hunger sneezing is a real thing

    The information about hunger sneezing in medical and scientific journals is sparse, probably because sneezing is thought to be an annoyance, but not a serious problem. Despite this, internet forums and Instagram comments reveal that many more people than expected resonate with Clea’s experience of stomach-related sneezing. It appears that the vagus nerve, which contacts a huge number of organs distant from the nose, could be the link we are looking for to understand triggers for sneezing. A deeper understanding about how our bodies communicate with and are controlled by our brains through the peripheral nervous system can provide important clues in our detective work to make sense of some of our bodies’ stranger responses and reactions.

References

1. Songu M, Cingi C (2009) Sneeze reflex: facts and fiction. Therapeutic Advances in Respiratory Disease, 3(3): 131-141
2. Teebi AS, Al-Saleh QA (1989) Autosomal dominant sneezing disorder provoked by fullness of stomach. Journal of Medical Genetics, 26: 539-40
3. Bhutta MF, Maxwell H (2009) Further cases of unusual triggers of sneezing. Journal of the Royal Society of Medicine, 102:49-50
4. Bhutta MF (2015) Sneezing induced by bladder fullness. International Journal of Urology, 22: 239
5. Bhutta MF, Maxwell H (2008) Sneezing induced by sexual ideation or orgasm: an under-reported phenomenon. Journal of the Royal Society of Medicine, 101:587-591
6. Breit S, Kupferberg A, Rogler G, Hasler G (2018) Vagus nerve as modulator of the brain-gut axis in psychiatric and inflammatory disorders. Frontiers in Psychiatry, 9(44):1-15
7. Drazen DL, Woods SC (2003) Peripheral signals in the control of satiety and hunger. Current Opinion in Clinical Nutrition and Metabolic Care, 6:621-629

Cover Image Source: news.sky.com