Have you ever walked out into bright sunlight and immediately felt a sneeze coming on? It’s a common experience for many, and you might be wondering, “Why Does The Sun Make Me Sneeze?” You’re not alone in this curious reaction. While it’s not a typical allergy, this phenomenon, known as the photic sneeze reflex, is a real and surprisingly common occurrence.
Like many others, I used to think sun sneezes were just a normal part of life. It wasn’t until I mentioned to my husband that I could trigger a sneeze by looking directly at the sun that I realized this wasn’t the case for everyone. His confused expression made it clear: sun sneezes are not universal. I was, in fact, experiencing something a bit unusual – but far from unique.
This light-induced sneezing is due to a harmless condition called the “photic sneeze reflex.” Even the ancient Greek philosopher Aristotle observed this quirk in the 4th century B.C., pondering, “Why does the heat of the sun provoke sneezing?” It wasn’t until 1954 that the medical community formally documented it. Scientists have even given it the memorable acronym ACHOO: Autosomal Dominant Compelling Helio-Ophthalmic Outburst Syndrome.
According to Louis Ptáček, a neurologist and human geneticist at the University of California, San Francisco, “It’s not a disease.” He explained to NewsHour that while some might find it bothersome, others see it as a quirky trait, even finding it helpful to “get a sneeze out.”
The photic sneeze reflex is characterized by sudden sneezing, often multiple times in a row, when someone moves from a dark environment into bright light. Sunlight is the most common trigger, but strong artificial light, like camera flashes, can also induce a sneeze. Interestingly, there’s a “refractory period” – a yet undetermined length of time one must spend in darkness before the light can trigger another sneezing fit.
It turns out, the photic sneeze reflex is surprisingly common, affecting an estimated 10 to 35 percent of the population. Its higher prevalence within families suggests a genetic component, specifically an autosomal dominant inheritance pattern, meaning only one parent needs to carry the gene for it to be passed on.
Is ACHOO in Your Genes?
A normal sneeze is a powerful reflex designed to protect our respiratory system. It’s how our bodies expel irritants and infectious agents from the nasal passages and lungs. Each sneeze can eject around 40,000 microscopic particles at an incredible speed – about 85 percent of the speed of sound. Quite a forceful expulsion!
“When we sneeze, there is a huge contraction of the diaphragm all at once,” Ptáček clarifies. He explains that irritants like dust or pepper particles in the nose irritate the mucous membranes, triggering the sneeze reflex as a protective mechanism against harmful environments.
But this still leaves us with the question: why does the sun make some of us sneeze? Is it an evolutionary quirk, perhaps a warning for those of us with fairer skin to avoid the sun’s harmful rays? (Probably not.)
The prevailing theory suggests a neurological “cross-wiring” issue. It’s thought that the signals between the trigeminal nerve, responsible for facial sensations like an itchy nose, and the optic nerve, which controls pupil constriction in response to light, get mixed up. The sudden bright light might overstimulate the optic nerve, and this signal inadvertently gets routed to the trigeminal nerve, tricking it into triggering a sneeze response as if there were an irritant in the nose.
However, comprehensive research into these theories is lacking. Most studies on the photic sneeze reflex are based on small groups or even single-family case studies.
Exploring the Science Behind Sun Sneezes
To further understand “why does the sun make me sneeze”, scientists have conducted some intriguing studies. A 2010 study in Switzerland, for example, used brain imaging to compare photic sneezers and non-sneezers. They discovered that photic sneezers showed greater activity in the primary and secondary visual cortex – brain regions processing visual information – when exposed to different light wavelengths. This supports the idea that the optic nerve and visual processing play a key role.
Conversely, Spanish researchers in 2016 examined the corneal nerves of individuals with photic sneeze reflex. They found that these individuals had thicker corneal nerves, which connect to the trigeminal nerve. However, it’s worth noting that all 13 participants in this study were from the same family, suggesting a potential genetic specificity within that family.
Ptáček, whose research focuses on the genetics of episodic disorders like migraines and epilepsy, has been collecting surveys on photic sneeze reflex for years. Despite the data gathered, in-depth analysis has been hindered by a lack of funding. Ptáček believes that the limited research is due to the perception of photic sneeze reflex as a minor issue. Funding tends to be directed towards more severe conditions like Parkinson’s and multiple sclerosis.
While generally harmless, the sneeze reflex triggered by bright light can pose risks in certain situations. The combination of temporary vision impairment from bright light, the sneeze itself, and the subsequent eye closure could be hazardous for individuals in specific professions. Case studies suggest potential risks for high-wire acrobats, baseball outfielders, and even combat pilots. On a more relatable level, anyone who has sneezed while driving out of a dark tunnel at highway speed knows it can be momentarily alarming.
Ptáček argues that further investigation into the photic sneeze reflex could unlock valuable insights into other, more complex reflex disorders. “If we knew one or more genes that cause photic sneeze reflex, I don’t doubt that that might teach us fundamental things about reflex disorders like epilepsy,” he suggests. He emphasizes that significant medical breakthroughs often arise from unexpected areas of research, even those seemingly unrelated to major diseases.
Keep Exploring Your Body’s Quirks
Understanding “why does the sun make me sneeze” not only satisfies our curiosity but also highlights the intricate and sometimes surprising workings of the human body. The photic sneeze reflex, while still not fully understood, serves as a reminder that even seemingly minor quirks can offer valuable clues to broader biological mechanisms. So, the next time you sneeze when stepping into the sunlight, remember you’re part of a significant group – and that your reaction is a fascinating area of ongoing scientific inquiry.
