Scratching the surface: Scientists crack the bacterial code on itch
28 Nov 2023 --- Researchers at Harvard Medical School uncover the mystery of itch. For the first time, they identify a common skin bacteria, Staphylococcus aureus (S. aureus), as the culprit behind the irritation. The findings, reported in the journal Cell, shed light on the relationship between microbes and skin, offering new ways intherapeutic interventions for eczema and dermatitis.
Contrasting previous beliefs associating itch with skin inflammation, the research reveals S. aureus induces the urge to scratch. “We know that many microbes, including fungi, viruses and bacteria, are accompanied by itch, but how they cause itch is not clear,” says senior author Isaac Chiu, associate professor of immunology at the Blavatnik Institute at HMS.
The harmony of microorganisms on the skin, disrupted in conditions like eczema and atopic dermatitis, allows S. aureus to thrive, provoking a molecular chain reaction that leads to persistent itch.
“We’ve identified an entirely novel mechanism behind itch — the bacterium S. aureus, which is found in almost every patient with chronic atopic dermatitis. We show that itch can be caused by the microbe itself,” continues Chiu.
Microbial twist to itch
Experiments on mice exposed to S. aureus demonstrated an intensifying itch over several days. The key player in this itch was identified as a bacterial enzyme, protease V8, released by S. aureus.
This enzyme triggers itch by activating a protein called PAR1 on skin neurons, initiating signals the brain interprets as an itch.
Till now, scientists knew many microbes accompany itch, but it was not clear how they caused itching (Image Credit: Harvard Medical School).
“When we started the study, it was unclear whether the itch resulted from inflammation,” shares Liwen Deng, a postdoctoral research fellow in the Chiu Lab.
“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.”
Neurons at root
To resolve the itch at the root, researchers interrupted the itch-scratch cycle by using an FDA-approved anti-clotting medicine.
The medicine successfully alleviated symptoms, relieving the need to scratch by blocking the activation of PAR1. The scientists report that the treatment also minimized skin damage.
They also suggest that the potential repurposing of this medicine opens doors for anti-itch treatments, such as using the active ingredient in the medicine for anti-itch topical creams.
Looking ahead, the scientists plan to explore whether other microbes play a role in triggering itch.
The new understanding of itch's microbial origin can change how skin care cosmetics are formulated for oral supplements and topical creams. It brings a more microbiome-focused approach to promoting skin health, targeting microbiome imbalances, such as atopic dermatitis, prurigo nodularis and psoriasis.
In recent microbiome-focused developments, HeiQ introduced a “synbiotic textile,” making it possible to wear skin care as clothing. The 100% biobased material slow-releases prebiotics and probiotics onto the skin.
Edited by Venya Patel
