To Dandruff Scientists, a Problem Itching for a Solution
Science has sent people to the moon; built an artificial heart; created genetically engineered, insect-resistant grains --and yet it finds some nuts hard to crack. Like, what exactly causes dandruff?
It’s been a real head-scratcher. Some scientists and doctors have posited that the unsightly flaking is caused by tiny yeasts that grow on people’s heads. Certainly, such yeasts do grow there. (The French scientist who first identified some of them more than 100 years ago, Louis Charles Malassez, has the dubious honor of having the fungi named after him.)
Others have suggested that dandruff is caused by inflammation of the scalp--leading to faster division of skin cells and a nice flaky environment that the yeasts simply love to grow on.
After all these years and who can guess how many billion flakes cascading down on imprudently selected black jackets, scientists still don’t know for sure--but it’s not for want of effort. Dandruff may not command the dollars thrown at cancer research or AIDS, but you’ll find hundreds of earnest and un-flaky articles on the topic in the dermatology journals. And there are whole labs dedicated to dandruff science, generally at companies that make anti-dandruff shampoos.
“Procter & Gamble has a real commitment to understand the biology of dandruff,” solemnly declares Thomas Dawson Jr., senior scientist in the Cincinnati company’s anti-dandruff laboratory. At any one time, he says, 30 to 40 scientists will be slaving away on dandruff studies--recruiting people with dandruff off the streets, taking swabs of their scalp flakes, washing their heads in this or that anti-dandruff formulation and carefully measuring changes in flake production.
Elsewhere at the company, microbiologists will be carefully coaxing the fungi found on flakes to grow in nutrients laced with heavy cream or olive oil (to mimic the oils of the scalp that these yeasts so adore). They’ll be using high-tech DNA methods to identify the fungi growing on heads and sophisticated lipid chemistry to pinpoint any changes in scalp oils.
Such single-minded dedication, at Procter & Gamble and elsewhere, appears to be bearing some fruit.
Dawson’s team, for instance, recently reported that the yeast long suspected to be a dandruff culprit is unlikely to be so. True, you can take some flakes off someone’s head and this yeast--Malassezia furfur--will grow up nicely on your cream- or oil-laden petri dishes.
But when Dawson’s team used DNA analysis to figure out what yeasts were in dandruff, they found hardly a trace of Malassezia furfur, while two other species--Malassezia restricta and Malassezia globosa--were abundant. The only reason that M. furfur shows up so often is because it can grow on the petri dishes. The other two yeasts are far too picky to sup on mere cream or olive oil: They want human grease.
What’s more, says Dawson, if you wash flaky scalps with anti-fungal shampoo, not only does the flaking die down, but these two fungi go away as well--implying they really are the culprits in dandruff.
Still, yeast isn’t everything. Scalp inflammation is probably central too. The yeasts, suggests Dawson, first take up residence on the scalp. They feast merrily on the oils on our heads, chopping them up into little fatty acids, ingesting the fatty acids they like and littering our scalps with the ones they can’t stand, like so many discarded banana peels or cheese rinds. One of these fatty acids--oleic acid--builds up on the scalp.
That, in turn, inflames the skin and sends it into cells-division overdrive. And presto! Dandruff results.
Even this can’t be the whole story because yeasts live on lots and lots of scalps and not everyone has dandruff.
Plus there’s a huge variation in dandruff severity (scientists have careful scales, or “scalp scores,” to measure degree of flaking). There must be something about different people’s heads that causes one person to end up with dandruff while another lucky chap’s pate doesn’t.
And dandruff waxes and wanes in unpredictable ways, notes Dr. David Voron, an Arcadia dermatologist and clinical professor of dermatology at USC’s Keck School of Medicine.
“It can go away for weeks and months--in some patients even for years,” he says. “And then it will just come back.”
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If you have an idea for a Booster Shots topic, write or e-mail Rosie Mestel at the Los Angeles Times, 202 W. 1st. St., Los Angeles, CA 90012, rosie.mestel@latimes.com.
