Scientists have discovered that itchiness could be due to a form of bacteria carried by one in three Americans.
Up until this point, scientists thought that persistent itching – which affects 15 percent of Americans – was related to other skin conditions like eczema, which are caused by inflammation.
But for the first time, researchers have shown that itching may be caused by a completely different mechanism.
In a first-of-its-kind study on mice and human cells, researchers at Harvard University found that a normally harmless strain of bacteria that lives in people’s noses and skin can invade skin cells and cause an uncontrollable urge to scratch.
Scientists from Harvard University found that itching from skin conditions like eczema could be due to the bacteria Staphylococcus aureus, which one in three Americans carries
The researchers said that ‘working like a pair of molecule scissors,’ an enzyme called V8 snips off part of the PAR1 protein that lines skin neurons. This causes PAR1 to release a signal through the skin neurons and up to the brain, which triggers the urge to scratch
Dr Isaac Chiu, study author and immunology professor at Harvard Medical School, said: ‘We’ve identified an entirely novel mechanism behind itch — the bacterium Staph aureus, which is found on almost every patient with the chronic condition atopic dermatitis. We show that itch can be caused by the microbe itself.’
These findings could inspire new topical treatments to stop chronic itching in people with skin conditions.
In conditions like eczema, the skin’s microbiome, or the healthy bacteria and oil that protect it, is thrown off balance, allowing harmful bacteria to flourish.
This includes Staphylococcus aureus, which is typically found on the skin or in the nose and is usually harmless.
The Centers for Disease Control and Prevention (CDC) estimate that one in three Americans carry Staphylococcus aureus in their noses.
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 on both arms in 14 healthy participants and 13 patients with eczema. Patients were between 18 and 58 years old.
They then exposed mice to Staphylococcus aureus, which caused them to develop an intense itch that worsened over several days and led to skin damage.
The team modified different versions of the Staphylococcus aureus microbe to find which enzymes were responsible for the itch. The bacteria typically invades the skin and releases 10 different enzymes.
The researchers said that ‘working like a pair of molecule scissors,’ an enzyme called V8 snips off part of the PAR1 protein that lines skin neurons.
This causes PAR1 to release a signal through the skin neurons and up to the brain, which triggers the urge to scratch.
The team also found that inflammatory white blood cells, which are activated in skin conditions like eczema and other allergies, don’t result in itching.
Dr Liwen Deng, lead study author and postdoctoral researcher in Dr Chiu’s lab, said: ‘When we started the study, it was unclear whether the itch was a result of 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 itch, but that the itch exacerbates inflammation on the skin.’
PAR1 helps blood clot, so the researchers gave itchy mice an FDA-approved anti-clotting medication to block PAR1 from initiating the cascade reaction. The desire to scratch diminished considerably, as did skin damage caused by itching.
This could lead to the development of a topical cream to stop this itching reaction and prevent lasting skin damage in people with conditions like eczema, which affects one in 10 Americans.
There are other theories for what causes itching in certain scenarios. For example, when the temperature changes drastically, the body releases histamines, which could cause itching.
The researchers also plan to test if 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 accompanied by itch, but how they cause itch is not clear.’
‘It’s a 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 do we itch and scratch? Does it help us, or does it help the microbe? That’s something that we could follow up on in the future.’
The study was published Wednesday in the journal Cell.
WHAT ARE STAPHYLOCOCCAL INFECTIONS?
Staphylococcal, or ‘staph’, infections are caused by the bacterium Staphylococcus.
These can cause relatively minor skin infections, such as boils, as well as serious ones affecting the blood, lungs and heart.
Most infections are caused by a group of bacteria called Staphylococcus aureus, which includes MRSA. MRSA is resistant to certain antibiotics.
Infections affecting the skin and soft tissue include:
- Boils – red, painful lumps that usually develop on the neck, face, armpits or buttocks
- Impetigo – causes sores, blisters and crusts; usually in children
- Skin abscesses – a collection of pus that appears as a painful lump under the skin’s surface
Invasive infections include:
- Endocarditis – infection of the inner heart lining, leading to fever, chest pain and coughing
- Pneumonia – lung infection that causes coughing, breathing difficulties and chest pain
- Sepsis – a violent immune response leads to fever, and a rapid breathing and heart rate
Around one in three people carry Staph bacteria harmlessly on their skin.
‘Staph’infections can cause red, painful boils that typically develop on the face
It only causes problems when it enters the body via cuts, grazes or medical equipment.
Although healthy people can be affected, those with weakened immune systems, such as due to a side effect of chemotherapy, are more likely to suffer.
Boils and other more minor forms of infection do not typically require treatment.
Antibiotics may be given or a minor procedure to drain pus from the skin.
For invasive infections, hospital treatment is required, which usually involves antibiotic injections over several days.
People can help to prevent Staph infections by:
- Washing their hands with soap and warm water frequently
- Keeping skin clean
- Not sharing towels, razors, bed linen or toothbrushes
- Keeping cuts clean and covered
Source: NHS Choices
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