Scientists have discovered that itching may be due to a form of bacteria carried by one in three Americans.
Until now, scientists thought that persistent itching in people with skin conditions such as eczema was due to inflammation.
But for the first time, researchers have shown that eczema-related itching may be caused by a completely different mechanism.
In a first-of-its-kind study in mice and human cells, researchers at Harvard University discovered that a normally harmless strain of bacteria that lives in the nose and skin of humans can invade skin cells and cause an uncontrollable urge to sensitize.manger.
Scientists from Harvard University discovered that the itching that occurs in patients with eczema may be due to the bacteria Staphylococcus aureus, which one in three Americans carry.
The researchers said an enzyme called V8 “acts like molecular scissors” and cuts off part of the PAR1 protein that lines skin neurons. This causes PAR1 to send a signal through the skin neurons and to the brain, triggering the urge to scratch
Dr. Isaac Chiu, study author and professor of immunology at Harvard Medical School, said: ‘We have identified a completely new mechanism behind itching: the bacterium Staph aureus, which is found in almost every patient with the chronic condition atopic dermatitis. We show that itching can be caused by the microbe itself.’
These findings could inspire new topical treatments to stop chronic itching in people with eczema and other conditions.
In patients with eczema, the skin’s microbiome, or the healthy bacteria and oils that protect it, becomes unbalanced, allowing harmful bacteria to flourish.
This also applies to Staphylococcus aureus, which is usually found on the skin or in the nose and is usually harmless.
The Centers for Disease Control and Prevention (CDC) estimates that one in three Americans carries Staphylococcus aureus in their nose.
It can lead to staph infections, which can cause skin infections, food poisoning and bacteremia, a bloodstream infection. They are also potentially fatal if they enter the bloodstream.
The research team swabbed the skin of both arms in 14 healthy participants and 13 patients with eczema. The patients were between 18 and 58 years old.
They then exposed mice to Staphylococcus aureus, causing them to experience intense itching that worsened over several days and led to skin damage.
The team modified different versions of the Staphylococcus aureus microbe to find out which enzymes were responsible for the itch. The bacteria typically penetrate the skin and release 10 different enzymes.
The researchers said an enzyme called V8 “acts like molecular scissors” and cuts off part of the PAR1 protein that lines skin neurons.
This causes PAR1 to send a signal through the skin neurons and to the brain, triggering the urge to scratch.
The team also found that inflammatory white blood cells, which are activated in skin conditions such as eczema and other allergies, do not lead to itching.
Dr. Liwen Deng, lead author of the study and postdoctoral researcher in Dr. Chiu, said: ‘When we started the study, it was unclear whether the itching was due to inflammation or not.’
‘We show that these things can be decoupled, that you don’t necessarily have to have inflammation for the microbe to cause itching, but that the itching worsens the inflammation on the skin.’
PAR1 helps blood clotting, so the researchers gave itchy mice an FDA-approved anticoagulant drug to prevent PAR1 from triggering the cascade reaction. The desire to scratch decreased significantly, as did skin damage due to itching.
This could lead to the development of a topical cream to stop this itching response and prevent permanent skin damage in people with eczema, which affects one in ten Americans.
There are other theories about what causes itching in certain scenarios. For example, when the temperature changes drastically, the body releases histamine, which can cause itching.
The researchers also plan to test whether other bacteria can lead to itching in patients with skin conditions.
Dr. Chiu said, “We know that many microbes, including fungi, viruses and bacteria, are associated with itching, but how they cause itching is not clear.”
“It’s speculation at this point, but the itch-scratch cycle could benefit the microbes and enable their spread to distant body sites and to uninfected hosts,” Dr Deng said.
‘Why itch and scratch? Does it help us, or does it help the microbe? That is something we can follow up on in the future.’
The research was published in the journal on Wednesday Cell.