- Itching is one of the most distressing and poorly understood symptoms of eczema.
- A recent study used animal models, human tissue, and nerve fibers to investigate the condition’s tendency to produce itching.
- The researchers concluded that the bacteria Staphylococcus aureus may be an important part of the puzzle.
- They hope their findings may eventually lead to treatments for a range of skin conditions.
Eczema, also called atopic dermatitis, is one of the most common skin conditions, affecting an estimated 223 million people globally.
One of the dominant symptoms is itch. While scratching can momentarily relieve the sensation, it can also cause skin damage, increase the risk of skin infections, and exacerbate inflammation.
“Itch plays a big part in the quality of life of people with eczema,” explained Carsten Flohr a professor at Kings College London and a member of the British Association of Dermatologists.
“It impacts both the quality of sleep and the amount of sleep people get. It also affects social and working life for adults, and the enjoyment of school for children,” Flohr told Medical News Today.
Andrew Proctor, the chief executive of the National Eczema, says eczema itching is a constant issue for people with the condition.
“For the millions of children and adults with atopic eczema, relentless itch is one of the most difficult things about living with this complex condition,” Proctor told Medical News Today.
“It often leads to the painful ‘itch-scratch cycle,’” he added, “where you scratch to relieve the itch, then the skin is damaged, and it becomes even more itchy, with even greater temptation to scratch.”
There are few long-term treatments that can reliably soothe this type of itching.
However, a recent study published in the journal Cell investigated how a particular skin microbe might drive itch in eczema. Experts hope the results could lead to new treatments.
The skin is considered to be the
It protects against pathogens, dehydration, mechanical damage, and ultraviolet light. It also carries receptors that provide sensations such as pain, temperature, and touch.
Importantly for eczema, it also contains receptors called
Like many other parts of the body, the skin is home to a thriving microbial community — the skin microbiome, which contains vast numbers of bacteria, fungi, and other microbes.
Although there is growing interest in the human microbiome, scientists have a long way to go before they understand its complex roles in health and disease.
“Your skin bacteria and skin immune system talk to each other and they talk to the bacteria in your gut. Just like with your gut, having a diverse balance is the key to a happy microbiome,” said Flohr, who wasn’t involved in the recent research.
Understanding how bacteria interact with each other as well as the skin and the immune system may one day help treat various skin conditions.
Medical News Today contacted one of the new study’s authors, Isaac Chiu, an associate professor of immunobiology at Harvard Medical School in Massachusetts. We asked why he decided to study skin microbes and eczema.
“My lab previously found that skin microbes can cause pain when under the skin’s surface. We wondered whether microbes also cause itch,” he said.
So, they investigated.
According to Chiu, research has shown that “S. aureus is one of the leading bacteria found on atopic dermatitis lesions.”
Evidence also suggests that S. aureus may help
However, until now, its links to itch were unclear.
The recent Cell study looks at this relationship in depth using animal models, human tissue, and nerve fibers.
The researchers initially applied S. aureus to the skin of mice, which they said increased the likelihood that the animals would develop dermatitis.
These mice also scratched much more than mice without S. aureus.
Next, the researchers set out to understand how S. aureus could trigger this itch response by focusing on enzymes produced by the bacteria. S. aureus produces 10 proteases, so the scientists focused on these.
Eventually, they identified protease V8 as the primary driver of the itch response: When the scientists injected V8 alone into mice, they started scratching.
As further evidence, the researchers showed that patches of human skin affected by eczema had higher levels of V8 than unaffected skin.
Finally, the scientists said they demonstrated that V8 could stimulate pruriceptor neurons from mice and humans by interacting with a specific receptor.
The receptor in question is proteinase-activated receptor 1 (PAR1). When the team blocked PAR1, it decreased itch and reduced skin damage caused by V8 and S. aureus.
V8 seems to be a particularly useful enzyme for S. aureus. Previous research shows “that V8 is important for many S. aureus processes,” Chiu explained.
“For example, it helps acquire nutrients, neutralizes immune factors, and cleaves proteins in the bloodstream,” he said.
The Federal Drug Administration (FDA) has already approved vorapaxar (ZONTIVITY), an oral drug that blocks PAR1 and helps prevent thrombotic cardiovascular events.
“Currently, there are only oral compounds available to block PAR1. There are no current topical formulations of these drugs,” Chiu said.
He hopes scientists will develop topical formulations, which might make a difference to people with eczema and other skin conditions that cause itch. However, he explains that widely available treatments like these will be a “long way” off.
Chiu and his colleagues are continuing to investigate. “We are still looking into the role of V8 in itch and skin inflammation,” he said.
“It’s possible that the scratching could induce inflammation and longer-term consequences, such as immune responses. I am also interested in other proteases from microbes and whether they could cause itch,” Chiu added.
Additionally, he plans to continue investigations into how PAR1 interacts with V8.
Flohr was upbeat about the future implications of these findings:
“This is an exciting discovery because it could open the doors to researchers finding new ways to treat eczema. For example, a drug that can block the enzyme that seems to be involved may be useful to treat itching,” he said.
