Until now, we’ve been blaming a fungus for dandruff, but your scalp's ecosystem might actually be upset by too much Staphylococcus.
Alice Klein

New Scientist
13 May 2016 - 10:03 AM  UPDATED 13 May 2016 - 10:03 AM

Here’s a head-scratcher. Could the species of bacteria living on your scalp determine whether you get dandruff?

Back in 1874, French microbiologist Louis-Charles Malassez suggested that a type of scalp-loving fungus – now known asMalassezia – is to blame for dandruff. This has been prevailing wisdom among many ever since, despite a lack of correlation between the amount of Malassezia living on people’s scalps and the presence and severity of dandruff.

But now researchers have bacteria in their cross hairs. Zhijue Xu of Shanghai Jiao Tong University in China and his colleagues have found that the presence of dandruff is more closely linked to excess growth of Staphylococcus bacteria.

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Head ecology

The researchers swabbed the scalps of 363 adults with and without dandruff, and used DNA sequencing to compare their fungal and bacterial profiles.

Surprisingly, the compositions of scalp fungi in the two groups were almost identical. In both cases, the Malassezia restricta strain comprised about 90 per cent of total scalp fungus.

But bacteria revealed a different story. People with dandruff had higher amounts of Staphylococcus, and much less of a different type of bacteria – Propionibacterium – than those who didn’t. Their findings suggest that the microbial balance on your head may determine whether you have dandruff.

Bacterial cure?

The scalps of dandruff sufferers also had less water on their surface, and smaller amounts of oily sebum secretions. But we don’t yet know which came first – does excess Staphylococcus lead to a dry scalp and dandruff, or do these conditions encourage Staphylococcus growth in the first place?

“That’s the bit that’s hard to unravel,” says Bernie Hudson of the University of Sydney, Australia. “There are probably lots of different factors at play.”

Finding out could lead to better treatments. Today, the most widely used dandruff remedy is zinc-pyrithione shampoo, which has antifungal properties, but is also known to kill Staphylococcus.

Xu says his team will now investigate methods for balancing Propionibacterium and Staphylococcus levels on the human scalp, which they hope might be a way to reduce dandruff.

Hudson agrees that this is an avenue worth exploring, but cautions that it may not be that simple. “Merely altering the concentration of one species of bacteria compared to another may not be therapeutic, because there could be other organisms that are also important,” he says. “But it’s definitely a good start.”

Journal reference: Scientific Reports, DOI: 10.1038/srep24877

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