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.

Pandemic vs. Epidemic: What’s the Difference?

If scientists can't develop a vaccine for a new virus quickly enough, an epidemic can turn into a pandemic.
If scientists can't develop a vaccine for a new virus quickly enough, an epidemic can turn into a pandemic.
doble-d/iStock via Getty Images

As the new coronavirus continues to spread around the world, the words epidemic and pandemic are showing up in news reports more often than they usually do. While the terms are closely related, they don’t refer to the same thing.

As the Association for Professionals in Infection Control and Epidemiology (APIC) explains on its website, “an epidemic occurs when an infectious disease spreads rapidly to many people.” Usually, what precedes an epidemic is an outbreak, or “a sudden rise in the number of cases of a disease.” An outbreak can affect a single community or several countries, but it’s on a much smaller scale than an epidemic.

If an epidemic can’t be contained and keeps expanding its reach, public health officials might start calling it a pandemic, which means it’s affected enough people in different areas of the world to be considered a global outbreak. In short, a pandemic is a worldwide epidemic. It infects more people, causes more deaths, and can also have widespread social and economic repercussions. The spread of the Spanish influenza from 1918 to 1919, which killed between 20 and 40 million people around the world, was a pandemic; more recently, the H1N1 influenza created a pandemic in 2009.

Here’s where it gets a little tricky: There’s no cut-and-dried classification system for outbreaks, epidemics, and pandemics. Based on the definitions above, it might seem like the current coronavirus disease, now called COVID-19, falls into the pandemic category already—according to a map from the World Health Organization (WHO), there are more than 80,000 confirmed cases in 34 countries, and nearly 2700 people have died from the disease. It’s also beginning to impact travel, stock markets, and the global economy as a whole. But WHO maintains that although the situation has the potential to become a pandemic, it’s still an epidemic for now.

“It really is borderline semantics, to be honest with you,” Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told CNN earlier this month. “I think you could have people arguing each end of it. Pandemics mean different things to different people.”

[h/t APIC.org]

Scotland Could Become the First Country to Provide Universal Period Products to Citizens

emapoket, iStock via Getty Images
emapoket, iStock via Getty Images

Fears over where to find—and how to afford—sanitary products before their next menstrual cycle may no longer be an issue for people in Scotland. Earlier today, as the BBC reports, Members of Scottish Parliament passed the first part of a bill that would make items like pads and tampons free to the public.

The Period Products Bill was first put forth in 2017 to address period poverty, which affects people who are unable to afford essential menstrual hygiene products. Pads, tampons, and some reusable menstrual items are currently available to students in primary schools and universities in the country. The Scottish government has also expanded the program to include additional public places and sports clubs, but this new bill goes even further. If passed, Scotland would become the first country to provide free period products to citizens on a universal scale.

Ministers in the Scottish Parliament were initially concerned about the bill's £24 million ($31 million) annual price tag, but earlier this month, members of all parties in the government came out in support of the legislation. Though the bill passed through the first stage of parliament today, February 25, the BBC wrote that "The government is expected to put forward a raft of amendments to address their 'significant' concerns about the legislation," including the aforementioned cost.

Period poverty is an issue that's felt around the world. In America, many lawmakers are fighting to end the "tampon tax": a sales tax that's added to sanitary products and waived from other hygiene products deemed essential in many states, like dandruff shampoo.

[h/t BBC]

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