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  • Here in this abundant forest, Malassezia is equipped with everything it could ever need.

  • Feasting constantly, it's in paradise.

  • But waitwhat's this?

  • In fact, Malassezia is a type of yeast that lives and dines on all of our scalps.

  • And in about half of the human population, its activity causes dandruff.

  • So, why do some people have more dandruff than others?

  • And how can it be treated?

  • We might consider ourselves individuals, but we're really colonies.

  • Our skin hosts billions of microbes.

  • Malassezia yeasts make themselves at home on our skin shortly after we're born.

  • Follicles, the tiny cavities that grow hairs all over our body, make for especially popular living quarters.

  • Malassezia are fond of these hideouts because they contain glands that secrete an oil called sebum that's thought to lubricate and strengthen our hair.

  • Malassezia evolved to consume our skin's proteins and oils.

  • And because of its many sebum-secreting follicles, our scalp is one of the oiliest places on our bodyand consequently, one of the yeastiest.

  • As these fungi feast on our scalp's oils, dandruff may form.

  • This is because sebum is composed of both saturated and unsaturated fatty acids.

  • Saturated fats neatly pack together.

  • Unsaturated fats, on the other hand, contain double bonds that create an irregular kink in their structure.

  • Malassezia eat sebum by secreting an enzyme that releases all of the oil's fatty acids.

  • But they only consume the saturated fats, leaving the unsaturated ones behind.

  • These irregularly shaped leftovers soak into the skin and pry its barrier open, allowing water to escape.

  • The body detects these breaches and responds defensively, causing the inflammation that gives dandruff its itch.

  • It also makes the skin cells proliferate to repair the damaged barrier.

  • Usually, our skin's outer surface, or epidermis, completely renews itself every two to three weeks.

  • Epidermal cells divide, move outwards, die, and form the skin's tough outer layer, which gradually sheds off in single cells far too small to see.

  • But with dandruff, cells churn out quickly to correct the broken barrier, meaning they don't mature and differentiate properly.

  • Instead, they form large, greasy clumps around the hair follicle that are shed as visible flakes.

  • This is how Malassezia's voracious appetite and our body's reaction to its by-products lead to dandruff.

  • Currently, the most effective way to get rid of dandruff is by using antifungals in things like shampoos, applied directly to the scalp, to kill Malassezia.

  • For those who experience dandruff, it usually comes and goes as sebum secretions vary throughout one's lifetime due to hormonal changes.

  • But despite the fact that Malassezia colonize everyone to a similar extent, not everyone gets dandruff.

  • Some people are more susceptible.

  • Exactly why is unclear.

  • Do people with dandruff have a certain genetic predisposition?

  • Is their skin barrier more permeable?

  • Scientists are currently investigating if people with dandruff do, in fact, lose more water through their scalps, and whether this is what's leading their skin cells to proliferate.

  • Researchers are learning that Malassezia communicate with our immune system using small, oily molecules called oxylipins that regulate inflammation.

  • If they can find a way to inhibit inflammatory oxylipins and boost anti-inflammatory ones, they could develop new treatments.

  • Scientists are also investigating if there's any benefit to our relationship with Malassezia.

  • They hypothesize that dandruff, which can be uncomfortable and embarrassing for us, creates a reliable, oily food source for the yeast.

  • But dandruff isn't contagious or a great threat to our health.

  • And Malassezia seem to excel at defending their territory, our skin, from other, more harmful microbes like Staphylococcus aureus.

  • So, while scientists have gotten to the bottom of many mysteries surrounding this condition, it must be said: dandruff remains a head-scratcher.

Here in this abundant forest, Malassezia is equipped with everything it could ever need.

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B2 US TED-Ed dandruff sebum skin unsaturated barrier

What causes dandruff, and how do you get rid of it? - Thomas L. Dawson

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    林宜悉 posted on 2021/10/15
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