Why Does Scratching Make Itching Worse?

iStock/champja
iStock/champja

It feels like a biological blooper: A persistent itch is made worse by scratching, the one thing that provides instantaneous relief. Evolutionary biologists have proposed that the relationship between scratching and itching developed when disease-carrying parasites and insects bit humans, causing itching skin; scratching brushed the bugs away. Anyone suffering from a mosquito bite can understand that connection.

There’s no simple answer for why skin that has just been scratched becomes even itchier, but researchers have identified some mechanisms behind the irritating phenomenon.

Why Scratching an Itch Doesn't Help

Our sensory neurons are constantly bombarded with stimuli, so some sensations take precedence over others. Sensory signals of one type can be overridden by signals of other types if the latter are strong enough. The overridden signals don’t even reach the brain—they’re stopped by specific neurons in the spinal cord. In this way, the pain caused by scratching is often sufficient to drown out the itch—but only temporarily.

Cells in the brain stem produce the neurotransmitter serotonin, which quells pain. But according to Zhou-Feng Chen, Ph.D., director of the Center for the Study of Itch at Washington University School of Medicine in St. Louis, Missouri, serotonin has an additional function. His group has found that as the serotonin spreads through the spinal cord, it can activate neurons that transmit itch signals to the brain, compelling us to scratch even more.

Each time we scratch, we put this cycle in motion. The increasing amount of serotonin may even make us scratch harder, until the urge to scratch becomes detached from any itch trigger on the skin. “It’s to try to suppress the itchy sensation, which occurs in your brain,” Chen tells Mental Floss. By this mechanism, itches can even become chronic.

Serotonin signaling isn’t the only way scratching worsens an itch; harm to the skin caused by scratching is another contributor. “When the skin barrier is irritated or further damaged, it releases certain pro-inflammatory factors that can directly aggravate itch by stimulating the sensory nerve fibers,” Brian Kim, M.D., co-director of the Center for the Study of Itch, tells Mental Floss. Those factors can also activate your immune system, and some types of immune cells around the affected area may produce chemicals that induce itch.

The very idea of scratching can also be a trigger. Chen’s research group reported last year that mice appear susceptible to scratching when they see other mice do the same. “Itching is actually contagious between people, between animals, and in your body itself,” Chen says. “When you scratch one place, you quickly want to scratch another area.” Scratching doesn’t just make itch more intense—it sometimes also causes the sensation to spread.

Relief for Itching

In mild cases, it may be possible to resist scratching through sheer force of will—but that’s not usually a long-term solution.

“I always feel bad because a lot of people say to patients, ‘Don’t scratch, don’t scratch,’ but that’s very challenging,” Kim tells Mental Floss. He says he tries to determine the cause of a person’s itchiness first. If it’s caused by an underlying medical problem, such as infestation with lice or liver disease, managing that issue may resolve the itch. Even if the underlying problem can’t be cured, there are medications that can calm itch in certain circumstances, such as antihistamines for allergy-induced itch and topical corticosteroids for itch caused by certain skin conditions, including eczema.

For now, drugs like these may be our best weapons against itching. “I think itch is often viewed as quirky, not serious, or embarrassing,” Kim says, which explains why there’s little research on itch despite its impact on our lives. Unfortunately, that coveted scratch in a bottle remains out of reach.

6 Dreaded Tasks That Are Actually Great For Managing Stress

iStock.com/gilaxia
iStock.com/gilaxia

High levels of the stress hormone cortisol can wreak havoc on your body. (According to a recent study on middle-aged adults, stress not only impairs memory but may even cause the brain to shrink!) Thankfully, some commonly dreaded activities can help reduce your frazzled state.

1. Washing the Dishes

According to a 2014 study published in the journal Mindfulness, a “mindful” approach to dishwashing could reduce stress. “A sample of 51 college students engaged in either a mindful or control dishwashing practice before completing measures of mindfulness, affect, and experience recall,” the study states. “Mindful dishwashers evidenced … increases in elements of positive affect (i.e., inspiration) [and] decreases in elements of negative affect (i.e., nervousness)." In other words, with the right mindset, zoning out in front of a sudsy sink is basically Nirvana.

2. Decluttering Your Home

Research suggests that clutter is more likely to stress out women. In 2010, a study in the Journal of Personality and Social Psychology looked to see how married couples dealt with (and felt about) messy homes [PDF]. “The wives in the study who perceived themselves as having a cluttered home or a home that needed work tended to have increased levels of cortisol throughout the day,” Emilie Le Beau Lucchesi wrote in The New York Times. "Those who weren’t feeling cluttered, which included most of the men in the study, had cortisol levels that tended to drop during the days.” So tidy up!

3. Exercising In A Group

Working out can feel like a chore, and exercising with a group can be a tad embarrassing—especially if you’re not on the same fitness level as everybody else. But according to research in the Journal of the American Osteopathic Association, exercising with a group is more beneficial at reducing stress than working out alone. “Researchers found that working out in a group lowers stress by 26 percent,” according to the press release. Go ahead and book that spin class!

4. Sniffing Your Partner’s Laundry

No sane person puts “sniff your significant other's dirty socks” on their to-do list, but perhaps they should. A 2018 study published in the Journal of Personality and Social Psychology shows that sniffing a loved one’s clothes can reduce stress. In the study, 96 women sniffed one of three scents—a neutral smell, their romantic partner’s scent, or the scent of a stranger. The stranger’s smell caused cortisol to spike. But their partner’s smell? It reduced stress.

5. Dwelling On Your Failures

The title of this study, which appeared in the journal Frontiers in 2018, says it all: “Writing About Past Failures Attenuates Cortisol Responses and Sustained Attention Deficits Following Psychosocial Stress.” According to the study, “[W]riting about a previous failure may allow an individual to experience a new stressor as less stressful, reducing its physiological and behavioral effects.” It sounds paradoxical, but the next time you're facing a crazy situation, just reflect on a time when it all went wrong—and things might not feel so bad.

6. Singing For All to Hear

For the shy and tone-deaf, singing in a group might be a anxiety-fueled nightmare—but they should try it anyway. A pilot study presented at the Society for Neuroscience conference last year showed that, in people with Parkinson's disease, singing in a group can reduce heart rate, blood pressure, and cortisol levels. (Researchers cautioned that this is preliminary data.) The findings jibe with a 2016 study from Drexel University that found, no matter your skill level, making art usually reduces cortisol levels [PDF].

Nearly Half of American Adults Don't Know Their Own Blood Type

iStock.com/nzphotonz
iStock.com/nzphotonz

If you know your blood type, you’re better off than nearly half of Americans. Of the 1004 adults in the U.S. who answered a recent Quest Diagnostics survey, only 57 percent said they knew whether they have type A, B, AB, or O blood.

This is roughly the same number of people who could recall their childhood phone number (55 percent), the survey revealed. By comparison, 74 percent of respondents remembered their lengthy Wi-Fi password, and 75 percent knew how much money was in their bank account.

For many, other personal health information was even murkier. Fewer than two in five people knew their cholesterol or blood sugar levels. Considering that these details provide important insights into one’s risk for certain diseases, survey administrators said this is a cause for concern.

“With consumers increasingly engaged in their own and their loved ones’ health care, it’s critical that they ‘know their numbers’—and have those numbers readily accessible—to ensure productive communication with their healthcare provider for both routine and critical care,” Cathy Doherty of Quest Diagnostics said in a press release.

With the exception of emergencies, at which time you may receive a universal donor's O-negative blood, doctors will almost always conduct blood typing and cross-matching tests to determine your blood type and identify minor antigens in your blood before conducting a transfusion or surgery.

It’s still important to know your blood type for other reasons. Newborn babies, for example, can develop hemolytic disease if their Rh blood type (meaning whether it's positive or negative) doesn’t match their mother's. And depending on your blood type, you may also have an increased risk for blood clots, heart disease, certain types of cancer, and even severe diarrhea and mosquito bites.

If you know your blood type, you’re also in a better position to donate blood and help people in need if there’s a natural disease or emergency, or if blood banks simply have a low supply. O blood tends to be the highest in demand (and O-positive is the most common blood type), but blood banks may issue public notices from time to time if they need a particular type.

If you’re unsure of your blood type, clinical labs like Quest Diagnostics offer blood type tests. You can also order test kits online from Amazon.

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