why do i sneeze in direct sunlight?

Question

Anytime i look near the sun i start to sneeze. Is this some kind of allergy?

i dont look directly into the sun! its just when i'm leaving the house or somewhere and the sun is facing me i just can't help but sneeze

Answer 1

photic sneeze reflex

An excellent question. This is far more complicated than you might imagine. Since the detailed answer below got kind of long, I will summarize the main points up front. About 25% of people do actually sneeze when exposed to bright lights like the sun. We do not know exactly why this happens, but it might reflect a "crossing" of pathways in the brain, between the normal reflex of the eye in response to light and the sneezing reflex. There is no apparent benefit from "sun-sneezing", and it probably is nothing more than an unimportant (but annoying) holdover of evolution.

There are actually three questions here:

1) Do people really sneeze when they look at the sun? This is an important question! There a lot of things that people say they do that they don�t really do. I personally do not sneeze when I look at the sun, and for a long time I thought this was a myth. But I am guessing that you are a sun-sneezer from your question. It seems that some people really do sneeze when they look at the sun, or actually at any bright light (there is nothing special about the sun). This has been recognized in medical journals for at least 40 years, and is called different things, including the "photic sneeze reflex" and even the "ACHOO syndrome". In a few instances the reflex has been documented by shining bright lights at people to make them sneeze, so it probably really does happen.

The thing is, the sun does not make most people sneeze. The best estimates are that only about 25% of people (i.e. 1 in 4) are sun-sneezers, and even sun-sneezers don�t do it most of the time. Other studies suggest that sun-sneezers might have inherited the trait in a dominant fashion from their parents (which means that if only one parent was a sneezer, they would pass the trait on to half of their kids). The problem with these estimates is that they generally rely on asking people if they sun-sneeze, and if their parents do. This is VERY unreliable. People who sun-sneeze tend to assume everyone does, and people who don�t sun-sneeze have often never even considered the possibility!!

2) What is the mechanism by which sun-sneezing occurs? What actually makes it happen? The simplest answer is that we don�t really know. There are many theories that I won�t get into specifically, since most require a detailed understanding of brain anatomy to even describe. What I will try to do instead is to briefly explain the nature of the sneeze reflex and offer a simple understanding of how light might act as a trigger.

What is a sneeze? Well, everybody knows what a sneeze is, but try and describe it sometime! The fact is, a sneeze is a very complicated thing, involving many areas of the brain. A sneeze is a reflex triggered by sensory stimulation of the membranes in the nose, resulting in a coordinated and forceful expulsion of air through the mouth and nose. A "reflex" means that some type of stimulation of your body causes you to react in a way that is NOT under your control, in other words you do it automatically without thinking and you can�t even stop it. Your body has many reflexes - the other one important to us here is called the "pupillary light reflex". If you shine a light in your eyes, your pupils get smaller, or constrict. You should be able to see this easily in a friend using a flashlight (or in the mirror).

In the pupillary light reflex, shining a light in the eye causes nerve signals to go from the eye to the brain and then back the eye again, telling the pupil to constrict. In the usual sneeze reflex, tickling the nose causes nerve signals to go from the nose to the brain and then back out to the nose, mouth, chest muscles and everything else involved in the actual sneeze. The key point is that the nerve signals take complicated routes through the brain, but usually the pupillary light reflex and sneeze reflex take different routes. Apparently what happens in sun-sneezers is that shining a bright enough light in the eye ALSO sends nerves signals from the eye to the brain and then back out to the nose, mouth and chest! In short, the wires are crossed a little bit in some people, and so shining a light in the eye "accidentally" activates two different outgoing pathways.

3) What is the benefit or value of sun-sneezing? Is it a good thing? Again, not an easy question! Some people argue that it must be a good thing since the trait has been maintained in our population. I�m not so sure.

What is the benefit of sneezing in general? The easy answer is that the thing tickling your nose might be a bad thing (like a virus, bacteria or pollen), and sneezing forces it out. The problem is that most adults sneeze mostly through their mouth, and so sneezing won�t force anything out of the nose. This is in contrast to most animals, who sneeze largely through their nose (watch your dog or cat next time). So I think that sneezing really serves little purpose to humans (little kids might be an exception to this). I think that sneezing is important to animals that rely heavily on the sense of smell, but that in us it is just an annoying "holdover" of evolution. But that is just my opinion.

But even if a normal sneeze does function in ridding the nose of foreign materials, I can think of no reason why shining a light in the eye would create a need to force things from the nose! And in the several papers I have read on this subject, no one else gave a reason why sun-sneezing would be beneficial. Sun-sneezing must truly either be an accident of brain anatomy, or an evolutionary holdover from our animal friends, that serves no purpose in humans.

Answer 2

WOW, some of these answers are great, a bit technical, but interesting and great.

I am a sun sneezer ;o) and so was my father. Figured it was hereditary. Just stands to reason. We were both sneezing our heads off every morning and mom would be fine. :oD

As far as a reason for it. The one writer above said it serves humans no purpose to clear nasal passages, maybe not the nasal passages, but it does seem to help clear my sinuses. Kind of gets things moving, so to speak. So I'd say it is beneficial.

I have allergies too, so this helps to clear my sinuses at the beginning of the day, after sleeping all night.

Think about it, how often do people sneeze when they are sleeping?

Perhaps another question for 'ask yahoo'. It might be on that sneezing site too. Anyway I certainly think its beneficial to me.

Happy Sneezing


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Good Life to you

Answer 3

Here's the best answer I've ever heard. All of your nerves are bundled up together in your spine and on up into your brain, and if any one nerve gets a big stimulus it can affect other ones. So when you first go out in the sun, your optic nerves get a big impulse of light, which tickles the olfactory nerves causing a sneeze. It happens to me, too!

I have also noticed if I eat nuts while looking at a computer screen, the screen seems to jump a little. Must be the same thing.

Answer 4

One of the triggers for sneezing is stimulation of the optic nerve. Bright lights provide that stimulation. (more in a minute...)

Sudden bright stimulation of the eye that occurs after a person has become adapted to darker surroundings is thought to bring on the condition, known as photic sneeze reflex.

The common photic sneeze reflex, which often creates multiple sneezes, is considered an inherited condition found more often in Caucasians.

A study reported by the British Journal of Ophthalmology noted that one form of the sneeze reflex appears related to another condition (nephropathic cystinosis) that causes abnormal crystal deposits on the clear front covering of the eye ( cornea). Nephropathic cystinosis, an inherited disease found mostly in Caucasians, is a metabolic condition affecting various parts of the body.

Answer 5

Here's a link to a podcast you can listen to called "The Body Odd." This episode is called "Sun Sneeze," and it talks about that.

Answer 6

In some people there is a sensitivity to sunlight which produces sneezing. Not that uncommon.

Answer 7

bcz when you squint your eyes you narrow your eustachian tubes (nasal passages) and this re-directs the moisture from your tear ducts. This moisture irritates the back of your nose and makes you sneeze. I read it in New Scientist or Scientific American a few years back! lol

Answer 8

It's a kind of allergy I suppose.

Answer 9

I don't know why but it does happen to me also. It's not an allergy I can tell you that.

Answer 10

don't look into the sun!