why do we sneeze when we look at bright light


Roberta A. Pagon, a professor of pediatrics at the University of Washington, explains. Reflexive sneezing induced by light, and sunlight in particular, is estimated to occur in 18 to 35 percent of the population and is known as the photic sneeze reflex (PSR) or the ACHOO (autosomal dominant compulsive helio-ophthalmic outbursts of sneezing) syndrome. Its genetic nature has been known for at least the last 25 years; it is periodically discussed in the medical literature and lay press. Observations that emerging from dim light into sunlight or turning to face directly into the sun commonly triggers the reflex prompted early inquiries into the trait. The number of induced sneezes–which seems to be genetically mediated and can be predicted within a family–is constant from episode to episode and typically numbers two or three. Some consequences of the PSR include danger to automobile drivers when emerging from dim light, such as a tunnel, into full sunlight, and disruption of outdoor group photos.


More recently, reports in publications oriented to military medicine have noted the potential danger to pilots experiencing the PSR. In fact, studies conducted by the military revealed that the PSR is not mediated by specific wavelengths of light and thus cannot be mitigated by the use of filtering lenses; rather the investigators concluded that the PSR is induced by changes in light intensity. Others have not found flickering light to precipitate the PSR. Exactly how sunlight causes some people to sneeze remains unknown.
It wouldnБt be a St. PatrickБs Day celebration in the Windy City without 400,000 spectators crowding the banks of the Chicago River to БoohБ and БaahБ at its (temporarily) emerald green tinge. But how do officials turn the water green? First, a bit of history: The dyeing tradition became an annual thing nearly 60 years ago, in 1962, but its real origins go back even further. In the early days of his administration as Mayor of Chicago, Richard J. Daley was a man on a mission to develop the cityБs riverfront area.


There was just one problem: The river itself was a sewage-filled. In order to get to the bottom of the cityБs pollution problem and pinpoint the exact places where waste was being discarded into the waterway (and by whom), Daley authorized the pouring of a special green dye into the river that would allow them to see exactly where dumping was occurring. Fast-forward to late 1961 when Stephen BaileyБpart of the Chicago Journeymen Plumbers Local, the cityБs St. PatrickБs Day Parade chairman, and a childhood friend of DaleyБsБwitnessed a colleagueБs green-soaked coveralls following a day of pouring DaleyБs dye into the Chicago River. That gave Bailey : If they could streak the Chicago River green, why not turn it all green? Three months later, revelers got their first look at an -colored river when the city poured 100 pounds of the chemical into the water. They got a really good look, too, as the river remained green for an entire week.

Over the next several years, the same practice was repeated, and again it was carried out by the Plumbers Local. The only difference was that the amount of dye used was cut in half over the next two years until they finally arrived at the : 25 pounds of dye = one day of green water. Unfortunately, the dye that was intended to help spot pollution was an oil-based fluorescein that many environmentalists was actually damaging the river even more. After fierce lobbying, eco-minded heads prevailed, and in 1966 the parade organizers began using a powdered, vegetable-based dye. While the exact formula for the orange powder (yes, it\’s orange until it\’s mixed with water) is kept top-secretБin 2003 one of the parade organizers a reporter that revealing the formula would be akin to Бtelling where the leprechaun hides its goldББthere are plenty of details that the committee lets even non-leprechauns in on. The dyeing process will at 9 a. m. on the morning of the parade, Saturday, March 17 (it\’s always held on a Saturday) when six members of the local Plumbers Union hop aboard two boats, four of them on the larger vessel, the remaining two on a smaller boat.

The larger boat heads out onto the water first, with three members of the crew using flour sifters to spread the dye into the river. The smaller boat follows closely behind in order to help disperse the substance. (The to catch a glimpse is from the east side of the bridge at Michigan Avenue, or on Upper and Lower Wacker Drive between Columbus and Lake Shore Drives. ) Approximately 45 minutes later, voila, the Chicago River is greenБbut donБt expect it to stay that way. These days, the color only sticks around for about. Which is roughly the same amount of time it takes to get a perfectly poured pint of Guinness if you venture out to an Irish pub on St. PatrickБs Day. Have you got a Big Question you\’d like us to answer? If so, let us know by emailing us at.

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