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.

A Generic EpiPen Coming in Early 2019 Could Save You Money

Brand-name EpiPens at a Congressional hearing on the escalating cost of the drug in 2016
Brand-name EpiPens at a Congressional hearing on the escalating cost of the drug in 2016
Alex Wong/Getty Images

For an incredibly common, life-saving medication, EpiPens (epinephrine auto-injectors) are surprisingly difficult for many consumers to get ahold of. Their cost has skyrocketed in recent years from less than $100 for a pack of two to more than $600. They’ve gotten so expensive that some EMTs have resorted to using syringes to manually administer epinephrine rather than purchasing the standard auto-injectors, which are almost exclusively made by the pharmaceutical company Mylan. Generic options have been slow to come to market, but according to Business Insider, a recently approved EpiPen rival is coming in the first few months of 2019, and it could save consumers a significant chunk of change.

The drug’s developers have had an unusually hard time getting the new EpiPen alternative, called Symjepi, onto store shelves. The drug was approved in 2017, but the company, Adamis Pharmaceuticals, had trouble finding investors. Now, Novartis, the Swiss-based pharmaceutical giant that manufactures drugs like Ritalin, is releasing the drug through its Sandoz division (perhaps most famous for it role in discovering LSD in the 1930s).

Symjepi will cost $250 out-of-pocket for a pack of two doses. That’s 16.6 percent less than the Mylan-authorized generic EpiPen or Teva’s generic EpiPen, which both sell for $300. It differs a bit from its rivals, though, in that it’s a pre-filled, single-dose syringe rather than a spring-loaded auto-injector. Auto-injectors are plastic, pen-like devices that keep the needle shielded until the moment of injection, and are specifically designed to help make it easier for untrained (even squeamish) people to use in an emergency. With this version, patients will need to remove a needle cap and inject the needle. Just like the EpiPen, though, it’s designed to be injected in the upper thigh, through clothing if necessary.

If you have health insurance, the difference in cost may not matter as much for you as a consumer, depending on your plan. (I personally picked up a two-pack of Mylan-authorized generic Epipens at CVS recently for $0, using a manufacturer’s Epipen coupon to knock down what would have been a $10 copay.) But it will matter considerably for those with high-deductible plans and to insurers, which, when faced with high costs, eventually pass those costs on to the consumer either through higher co-pays or higher premiums. It also affects agencies that buy EpiPens for emergency use, like local fire departments. And since EpiPens expire after just a year, the costs add up.

However, there’s currently a shortage of EpiPens on the market, according to the FDA, making it more important than ever to have other epinephrine drugs available to those at risk for serious allergic reactions.

[h/t Business Insider]

Brain-Eating Amoeba Kills Seattle Woman Who Used Tap Water in Her Neti Pot

CDC/Dr. Govinda S. Visvesvara, Wikimedia Commons // Public domain
CDC/Dr. Govinda S. Visvesvara, Wikimedia Commons // Public domain

If you use a neti pot to clear out your sinuses, there's one important rule you should always follow: Don't fill it with tap water. Doing so could land you a sinus infection, or worse, a potentially fatal disease caused by a brain-eating amoeba. Although the latter scenario is exceptionally rare, a 69-year-old woman in Seattle died from doing just that, The Seattle Times reports. Experts are also warning that these infections could become more common as temperatures in the northern hemisphere continue to rise.

Physicians at Seattle's Swedish Medical Center initially thought the woman had a brain tumor. She was brought into the emergency room following a seizure, and a CT scan of her brain seemed to reveal a tumor-like mass. The only other known symptom she had was a red sore on her nose, which was previously misdiagnosed as rosacea. When surgeons operated on her the following day, they noticed that "a section of her brain about the size of a golf ball was bloody mush," neurosurgeon Dr. Charles Cobbs told The Seattle Times. "There were these amoeba[e] all over the place just eating brain cells. We didn't have any clue what was going on, but when we got the actual tissue we could see it was the amoeba."

She died a month later of an infection called granulomatous amoebic encephalitis (GAE), according to a recent case report published in the International Journal of Infectious Diseases. The disease is caused by a single-celled amoeba called Balamuthia mandrillaris, and it's extremely deadly. Of the 109 cases between 1974 and 2016, 90 percent were fatal.

According to the FDA, some bacteria and amoebae in tap water are safe to swallow because acid in the stomach kills them. However, when they enter the nasal cavity, they can stay alive for long periods of time and travel up to the brain, where they start eating their way through tissue and cells. Another brain-eating amoeba called Naegleria fowleri can cause a similar disease, except it acts faster and can cause death in just a few days. Although it's also rare, it's usually found in warm freshwater, and infections start by getting contaminated water up one's nose while swimming or by using a nose irrigation device filled with tap water.

Dr. Cynthia Maree, an infectious disease doctor at the Swedish Medical Center, said the changing environment could facilitate the spread of these infections. "I think we are going to see a lot more infections that we see south (move) north, as we have a warming of our environment," Maree says. Researchers say these amoebae are still little-understood. Future studies would need to be conducted to learn more about the risk factors involved.

[h/t The Seattle Times]

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