Photic sneeze reflex is a condition triggered by exposure to bright light. Around 35% of the population has this reflex.

Sneezing is a natural response that removes irritants from your nose. But while it’s common to sneeze with a cold or allergies, some people also sneeze when exposed to bright light and other stimuli.

Photic sneeze reflex is also known, somewhat humorously, as autosomal dominant compelling helio-ophthalmic outburst (ACHOO syndrome). It’s a condition characterized by successive sneezing induced by bright light.

This is different from a normal sneeze, which is triggered by an infection or an irritant.

Photic sneeze reflex affects about 11 to 35 percent of the population, yet it isn’t well studied. According to a 1995 study in the Journal of the American Optometric Association, the majority of photic sneezers are female and white.

Photic sneeze reflex is an inherited, genetic trait. But since sneezing is a regular occurrence, it’s possible to have this trait without realizing it.

It’s also a dominant trait. If one of your parents has this reflex, you have a 50 percent chance of inheriting ACHOO syndrome, too.

The gene responsible for photic sneezing hasn’t been identified. But if you have the trait, you’ll likely sneeze multiple times in response to bright light. The number of sneezes could be as little as two or three, but some people report as many as 40 or more successive sneezes.

The way the reflex manifests in you might differ from those in your family.

It’s important to note that while bright light can bring on ACHOO syndrome, the reflex isn’t trigged by light itself, but by a change in light intensity.

Sitting in a brightly lit house might not trigger a sneeze. But you may start sneezing if you step into direct sunlight. Similarly, if you’re driving through a tunnel on a bright, sunny day, you might start sneezing upon exiting the tunnel.

Even though this sneeze reflex is inherited, some researchers believe it’s also possible to acquire it, although more research is needed.

The 1995 study found that fewer than 27 percent of photic sneezers interviewed were able to recall a parent with the same sneeze reflex.

The same study, however, did find a link between photic sneezing and a deviated nasal septum.

The actual cause of photic sneeze reflex is unknown.

One theory is that sneezing involves the optic nerve. A change in light may stimulate this nerve, creating the same sensation as having an irritant in the nose. This sensation could possibly be responsible for the sneeze.

Another theory is that light exposure causes eye tears, which briefly empty into the nose. This might also cause temporary irritation in the nose and sneezing.

It’s not only a change in light that can trigger the sneeze reflex. Some people with photic sneeze reflex are also sensitive to other types of stimuli.

For example, if you have a history of photic sneeze reflex, receiving an eye injection — such as anesthesia prior to eye surgery — may trigger a sneeze or two.

This is because an eye injection can stimulate the trigeminal nerve. This nerve provides sensation to your face, and it also signals the brain to sneeze.

Some people even have successive sneezes after eating. This can happen after eating spicy foods or a large meal. Spicy foods may trigger sneezing as receptors in your nose detect capsaicin, a chili pepper extract.

The cause of successive sneezing from a full stomach is unknown, but it doesn’t appear to be related to food allergy.

Photic sneezing in itself isn’t harmful to your health. It’s a known condition, yet there aren’t any medications or surgical procedures to stop the reflex.

To avoid sneezing, some people shield their eyes before exposure to the sun and other bright lights by wearing sunglasses, scarves, or even a hat.

While photic sneezing isn’t related to allergies, taking an over-the-counter antihistamine may reduce the reflex in people who have seasonal allergies.

Photic sneeze reflex can be dangerous in some situations, such as when operating a car or other motor vehicle. Sudden exposure to bright light could trigger successive sneezing, affecting your ability to maintain control of a car.

Because sneezing causes involuntary eye closure, multiple sneezes while driving could cause a traffic accident. Photic sneeze reflex can also pose a danger to airplane pilots.

If an eye injection triggers a sneeze reflex, you may start sneezing as a doctor injects medicine into your eye before surgery or another procedure. If the needle isn’t removed in time, you may have permanent or temporary eye damage.

If you have photic sneeze reflex and have concerns about these risks, talk to your doctor about how to minimize them.

Photic sneeze reflex is a condition triggered by exposure to bright light.

The next time you head outside on a sunny day, see if you let out a sneeze or series of sneezes. Your reaction might be due to allergies, or it might be the change in light. If you have the reflex, you probably inherited the trait from a parent.

There’s no need to worry about this reflex unless it gets in the way of your safety. If this is the case, your doctor may be able to suggest management techniques that involve anticipating changes in light or being held in position if receiving an eye injection.