Why Is Your First Instinct After Hurting Your Finger to Put It in Your Mouth?

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If you close your fingers in a car door or slam your funny bone into a wall, you might find your first reaction is to suck on your fingers or rub your elbow. Not only is this an instinctive self-soothing behavior, it's a pretty effective technique for temporarily calming pain signals to the brain.

But how and why does it work? To understand, you need to know about the dominant theory of how pain is communicated in the body.

In the 17th century, French scientist and philosopher René Descartes proposed that there were specific pain receptors in the body that "rang a bell in the brain" when a stimulus interacted with the body, Lorne Mendell, a professor of neurobiology and behavior at Stony Brook University in New York, tells Mental Floss. However, no study has effectively been able to identify receptors anywhere in the body that only respond to painful stimuli.

"You can activate certain nerve fibers that can lead to pain, but under other circumstances, they don't," Mendell says. In other words, the same nerve fibers that carry pain signals also carry other sensations.

In 1965, two researchers at MIT, Patrick Wall and Ronald Melzack, proposed what they called the gate control theory of pain, which, for the most part, holds up to this day. Mendell, whose research focuses on the neurobiology of pain and who worked with both men on their pain studies, explains that their research showed that feeling pain is more about a balance of stimuli on the different types of nerve fibers.

"The idea was that certain fibers that increased the input were ones that opened the gate, and the ones that reduced the input closed the gate," Mendell says. "So you have this idea of a gate control sitting across the entrance of the spinal cord, and that could either be open and produce pain, or the gate could be shut and reduce pain."

The gate control theory was fleshed out in 1996 when neurophysiologist Edward Perl discovered that cells contain nociceptors, which are neurons that signal the presence of tissue-damaging stimuli or the existence of tissue damage.

Of the two main types of nerve fibers—large and small—the large fibers carry non-nociceptive information (no pain), while small fibers transmit nociceptive information (pain).

Mendell explains that in studies where electric stimulation is applied to nerves, as the current is raised, the first fibers to be stimulated are the largest ones. As the intensity of the stimulus increases, smaller and smaller fibers get recruited in. "When you do this in a patient at low intensity, the patient will recognize the stimulus, but it will not be painful," he says. "But when you increase the intensity of the stimulus, eventually you reach threshold where suddenly the patient will say, 'This is painful.'"

Thus, "the idea was that shutting the gate was something that the large fibers produced, and opening the gate was something that the small fibers produced."

Now back to your pain. When you suck on a jammed finger or rub a banged shin, you're stimulating the large fibers with "counter irritation," Mendell says. The effect is "a decrease in the message, or the magnitude of the barrage of signals being driven across the incoming fiber activation. You basically shut the gate. That is what reduces pain."

This concept has created "a big industry" around treating pain with mild electrical stimulation, Mendell says, with the goal of stimulating those large fibers in the hopes they will shut the gate on the pain signals from the small fibers.

While counter irritation may not help dull the pain of serious injury, it may come in handy the next time you experience a bad bruise or a stubbed toe.

Why You Should Never Flush Your Contacts Down the Drain

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When a pair of contact lenses reach the end of their short life span, it may be tempting to dump them—and the liquid they’re stored in—down the bathroom sink drain. As The Atlantic points out, though, this is bad for the environment.

However small and thin they may be, contact lenses can contribute to microplastic pollution in waterways when they’re not disposed of properly, according to a new study presented at the recent American Chemical Society national meeting in Boston. The study surveyed contact lens users and non-users, and found that 19 percent of users flush the lenses down the toilet or sink drain instead of placing them in the trash. That translates to about 3 billion contact lenses per year, Rolf Halden, a researcher at Arizona State University and one of the study's authors, told The Atlantic.

Halden said he was inspired to look into the issue out of personal interest—he, too, wears contact lenses—and because he couldn’t find any studies on what happens to lenses after they’re flushed down the drain. Halden and his team discovered that the lenses end up in wastewater, where they can sink to the bottom because they are denser than water. There, they could endanger aquatic life, especially bottom feeders that may ingest the particles.

Researchers also found that microbes in wastewater treatment plant systems can degrade the structure of the lenses themselves and break them into tinier pieces. In the larger environment, those bits could be consumed by every organism in the local food chain. In addition, some of the flushed lenses are turned into a treated sewage sludge that is ultimately used to fertilize crops, so the waste could end up in our soil and affect creatures like earthworms. The extent to which this affects humans' food supply is not currently known.

"Ultimately, we hope that manufacturers will conduct more research on how the lenses impact aquatic life and how fast the lenses degrade in a marine environment,” Halden says in a statement.

So the next time you’re done using your contact lenses, think of the fish and worms, and throw them in the trash instead.

[h/t The Atlantic]

Debunking 6 Common Home Remedies That Aren't Worth Trying

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While it’s never fun—or cheap—to go to the doctor, sometimes you just have to bite the bullet and make an appointment. While you may read a slew of articles online during your middle-of-the-night WebMD binge, the “natural” home remedies that some blogs swear by are often at best no better than placebos, and at worst actively harmful.

A new video from SciShow explores several home “remedies” that don’t actually help treat common medical issues. The nine-minute video debunks some of the "natural" treatments that people often cite as cures for ailments as benign as allergies or as serious as poisoning. Spoiler: Most of them have no scientific basis.

If, for instance, you’ve ever heard the idea that local honey can act as an allergy cure, put down the spoon. Despite being delicious, honey doesn’t provide enough exposure to the allergens that cause those sniffles and itches to help. When your seasonal allergies hit, take medication or visit an allergist instead.

How about the old custom of putting butter on a burn? Unsurprisingly, fatty foodstuffs don’t make great wound treatments. While people used to believe that burns shouldn’t be exposed to air, oily substances like butter will actually trap heat from your burn, making it worse. The key to treating a burn is cooling it off. You want to stick it in cool water, not warm butter.

If you are unlucky enough to catch head lice, you're probably willing to try whatever you can get your hands on to destroy the little critters. But that pricey medicated shampoo really is the best way to go. Scientists have found that washing your hair with vinegar isn’t the answer. Researchers have found that lice nesting in hair aren’t affected by vinegar, even when the hair in question is soaked for 8 hours.

Some of these home remedies seem a little out-there, but others are understandable. Ipecac syrup once had a place on every pharmacy shelf as a method of treating people who ingested poison. The syrup is poisonous itself, and it makes you vomit—but vomiting isn’t a guarantee that your body has rid itself of all the toxins, and it might just make it harder for your doctor to diagnose what’s going on. Poison Control no longer recommends keeping ipecac syrup on hand, and U.S. manufacturers stopped making it in 2010.

Tilting your head back to staunch a nosebleed is yet another common treatment that can backfire on you. Tilting your head back does stop the blood from flowing from your nose. But it means that your blood will flow down your throat instead of out your nose. So instead of getting a towel bloody, you put yourself at risk of choking on your own blood.

The last “remedy” SciShow tackles isn’t directly harmful, but it won’t help, either. Some people recommend treating pink eye by using warm chamomile tea bags as eye compresses. While chamomile does have some anti-inflammatory properties, there’s no evidence that chamomile is at all effective in treating pink eye. Draping warm tea bags over your eyes probably won’t harm you, and in fact, the heat may relieve some pain, but the tea itself isn’t going to cure you.

Dive into the facts behind these “remedies” in the video below. And remember: when in doubt, always go to the doctor.

[h/t Digg]

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