The same bacteria that commonly cause acne may also help prevent dandruff, highlighting the role of the microbiome in managing both skin conditions.
Dandruff is often caused by too much of the fungus Malassezia restricta disturbing skin renewal, making cells on the scalp cluster together and form white flakes. It is commonly treated with chemicals that kill M. restricta, but the dandruff returns when the treatment stops.
To find a more lasting therapy, Viduthalai Regina at the Singapore Centre for Environmental Life Sciences Engineering and his colleagues focused on resetting the microbiome.
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The team looked at 65 volunteers, 32 of whom had dandruff. They were all given the same shampoo to use for three weeks as a sort of washout period between any previous treatments and starting the new investigation. The team then looked at the microbial compositions of their hair follicles and scalps.
The most abundant species in the scalp microbiome among those without dandruff was Cutibacterium acnes, which is thought to play a role in acne. C. acnes also produces propionic acid, which appears to keep M. restricta at bay. In the dandruff group, the most abundant microbes were in the Malassezia fungi group.
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The team also found that the microbiomes within an individual’s scalp and hair follicles were similar, suggesting that bacteria originate in hair follicles and spread to the scalp.
In another part of the experiment, which was partly funded by L’Oreal, the researchers looked at 57 people with moderate to severe dandruff. Some were told to use a lotion containing propionic acid alongside the shampoo two to three times a week for up to 28 days. The rest were given a control lotion.
“Application of propionic acid helped reset the [biome] community balance and led to alleviation of dandruff symptoms,” the team writes in the paper.
Yousuf Mohammed at the University of Queensland in Brisbane, Australia, says the research is compelling, especially because tests were conducted both in the lab and on people.
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The paper demonstrates how important it is to fix the underlying conditions that cause dandruff, otherwise it becomes a cycle where the growth of the fungus is promoted, he says.
“Applying propionic acid tips the balance towards C. acnes,” says Mohammed. “So if you break the cycle at the right point, then the rate of growth of the fungus can’t get out of control.”
Reflecting on the role of C. acnes in dandruff, Mohammed says: “It’s amazing how nature works. C. acnes has a very important, healthy role in hair follicles, but then in acne, when the pores are blocked, it’s a pathogenic bacteria.”
Reference:
bioRxiv DOI: 10.1101/2024.05.02.592279
