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Why Does Light Help Some People Sneeze?

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When you feel a sneeze building up but it doesn’t seem to want to come out, you may have heard the advice to look into a light. The idea is that it’s supposed to trigger a reflex that makes you sneeze, and it turns out this happens to be based more in science than urban legend.

Seventeen to 35 percent of the population is estimated to be prone to the photic sneeze reflex (PSR), also known as—no joke—ACHOO (autosomal dominant compulsive helio-ophthalmic outbursts of sneezing) syndrome. PSR is reflexive sneezing set off by light, especially light from the sun. Why this occurs has been puzzling scientists for millennia. Aristotle suspected that it was the heat from the sun on someone’s nose that brought on the sneezing. Francis Bacon tested this theory 2,000 years later by walking into the sunlight with his eyes closed to find that heat alone wasn’t enough to cause the reaction. He surmised that when the light made someone's eyes water, that moisture leaked into the nose and irritated it to the point of sneezing. This hypothesis wasn’t too far-out, considering that sneezes are usually induced by irritants in the nose, but today scientists believe that the phenomenon has more to do with our brains than our noses.

You sneeze when your brain’s trigeminal nerve, the nerve responsible for your face’s sensations and movements, senses irritants like dust or hair in your nose. This nerve lies close to the optic nerve, which senses vision. If your optic nerve senses a sudden transition from dim light to bright light, it responds by constricting the eye’s pupils. For people affected by PSR, it’s believed that this signal gets misinterpreted by your trigeminal nerve, resulting in a sneeze. Individuals sensitive to light-induced sneezing have their parents to thank. The trait is autosomal-dominant, meaning it doesn’t show up on the X or Y chromosome. All it takes is one copy of the gene for the trait to be expressed, so if one parent has PSR there’s a 50/50 chance their child will too.

ACHOO may sound like a silly condition (for several reasons), but it can have some real-life implications. Because a sneeze is accompanied by momentary loss of vision, a sunny day could prove problematic for tightrope walkers, outdoor athletes, and even automobile drivers with the syndrome. One 1993 essay published in the journal Military Medicine brought up the point that this phenomenon could be life-threatening to fighter pilots. Fortunately, it was discovered that this could be avoided with a basic pair of sunglasses.

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What’s the Difference Between Prison and Jail?
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Many people use the terms jail and prison interchangeably, and while both terms refer to areas where people are held, there's a substantial difference between the two methods of incarceration. Where a person who is accused of a crime is held, and for how long, is a factor in determining the difference between the two—and whether a person is held in a jail or a prison is largely determined by the severity of the crime they have committed.

A jail (or, for our British friends, a gaol) refers to a small, temporary holding facility—run by local governments and supervised by county sheriff departments—that is designed to detain recently arrested people who have committed a minor offense or misdemeanor. A person can also be held in jail for an extended period of time if the sentence for their offense is less than a year. There are currently 3163 local jail facilities in the United States.

A jail is different from the similarly temporary “lockup”—sort of like “pre-jail”—which is located in local police departments and holds offenders unable to post bail, people arrested for public drunkenness who are kept until they are sober, or, most importantly, offenders waiting to be processed into the jail system.

A prison, on the other hand, is usually a large state- or federal-run facility meant to house people convicted of a serious crime or felony, and whose sentences for those crimes surpass 365 days. A prison could also be called a “penitentiary,” among other names.

To be put in a state prison, a person must be convicted of breaking a state law. To be put in a federal prison, a person must be convicted of breaking federal law. Basic amenities in a prison are more extensive than in a jail because, obviously, an inmate is likely to spend more than a year of his or her life confined inside a prison. As of 2012, there were 4575 operating prisons in the U.S.—the most in the world. The country with the second highest number of operating prisons is Russia, which has just 1029 facilities.

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What Do Morticians Do With the Blood They Take Out of Dead Bodies?
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Zoe-Anne Barcellos:

The blood goes down the sink drain, into the sewer system.

I am not a mortician, but I work for a medical examiner/coroner. During an autopsy, most blood is drained from the decedent. This is not on purpose, but a result of gravity. Later a mortician may or may not embalm, depending on the wishes of the family.

Autopsies are done on a table that has a drain at one end; this drain is placed over a sink—a regular sink, with a garbage disposal in it. The blood and bodily fluids just drain down the table, into the sink, and down the drain. This goes into the sewer, like every other sink and toilet, and (usually) goes to a water treatment plant.

You may be thinking that this is biohazardous waste and needs to be treated differently. [If] we can’t put oil, or chemicals (like formalin) down the drains due to regulations, why is blood not treated similarly? I would assume because it is effectively handled by the water treatment plants. If it wasn’t, I am sure the regulations would be changed.

Now any items that are soiled with blood—those cannot be thrown away in the regular trash. Most clothing worn by the decedent is either retained for evidence or released with the decedent to the funeral home—even if they were bloody.

But any gauze, medical tubing, papers, etc. that have blood or bodily fluids on them must be thrown away into a biohazardous trash. These are lined with bright red trash liners, and these are placed in a specially marked box and taped closed. These boxes are stacked up in the garage until they are picked up by a specialty garbage company. I am not sure, but I am pretty sure they are incinerated.

Additionally anything sharp or pointy—like needles, scalpels, etc.—must go into a rigid “sharps” container. When they are 2/3 full we just toss these into one of the biotrash containers.

The biotrash is treated differently, as, if it went to a landfill, then the blood (and therefore the bloodborne pathogens like Hepatitis and HIV) could be exposed to people or animals. Rain could wash it into untreated water systems.

This post originally appeared on Quora. Click here to view.

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