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

12,772,950 views ใƒป 2021-02-09

TED-Ed


ืื ื ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ืœืžื˜ื” ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ.

ืชืจื’ื•ื: Ido Dekkers ืขืจื™ื›ื”: zeeva livshitz
00:07
Here in this abundant forest,
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ืคื” ื‘ื™ืขืจ ื”ืขื‘ื•ืช ื”ื–ื”,
00:09
Malassezia is equipped with everything it could ever need.
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ืžืœืกื–ื™ื” ืžืฆื•ื™ื™ื“ืช ื‘ื›ืœ ืžื” ืฉื”ื™ื ืื™ ืคืขื ืชืฆื˜ืจืš.
00:13
Feasting constantly, itโ€™s in paradise.
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ื”ื™ื ืื•ื›ืœืช ื›ืœ ื”ื–ืžืŸ, ื–ื” ื’ืŸ ืขื“ืŸ.
00:16
But waitโ€” whatโ€™s this?
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ืื‘ืœ ื—ื›ื• -- ืžื” ื–ื”?
00:18
In fact, Malassezia is a type of yeast that lives and dines
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ืœืžืขืฉื”, ืžืœืกื–ื™ื” ื”ื™ื ืกื•ื’ ืฉืœ ืฉืžืจื™ื ืฉื—ื™ื™ื ื•ืกื•ืขื“ื™ื.
00:23
on all of our scalps.
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ืขืœ ื”ืงืจืงืคื•ืช ืฉืœ ื›ื•ืœื ื•
ื•ื‘ืขืจืš ื‘ื—ืฆื™ ืžื”ืื•ื›ืœื•ืกื™ื” ื”ืื ื•ืฉื™ืช ื”ืคืขื™ืœื•ืช ืฉืœื”ื ื’ื•ืจืžืช ืœืงืฉืงืฉื™ื.
00:26
And in about half of the human population, its activity causes dandruff.
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00:31
So, why do some people have more dandruff than others?
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ืื–, ืœืžื” ืœื—ืœืง ืžื”ืื ืฉื™ื ื™ืฉ ื™ื•ืชืจ ืงืฉืงืฉื™ื ืžืื—ืจื™ื?
00:35
And how can it be treated?
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ื•ืื™ืš ืืคืฉืจ ืœื˜ืคืœ ื‘ื”ื?
00:37
We might consider ourselves individuals, but weโ€™re really colonies.
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ืื ื—ื ื• ืื•ืœื™ ื—ื•ืฉื‘ื™ื ืขืœ ืขืฆืžื ื• ื›ืื™ื ื“ื™ื‘ื™ื“ื•ืืœื™ื, ืื‘ืœ ืื ื—ื ื• ืœืžืขืฉื” ืงื•ืœื•ื ื™ื•ืช.
00:41
Our skin hosts billions of microbes.
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ื”ืขื•ืจ ืฉืœื ื• ืžืืจื— ืžื™ืœื™ืืจื“ื™ ืžื™ืงืจื•ื‘ื™ื.
00:45
Malassezia yeasts make themselves at home on our skin shortly after weโ€™re born.
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ืฉืžืจื™ ืžืœืกื–ื™ื” ืขื•ืฉื™ื ืืช ื‘ื™ืชื ืขืœ ืขื•ืจื™ื ื• ืžืขื˜ ืื—ืจื™ ืฉืื ื—ื ื• ื ื•ืœื“ื™ื.
00:51
Follicles, the tiny cavities that grow hairs all over our body,
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ื–ืงื™ืงื™ื, ื”ืฉืงืขื™ื ื”ื–ืขื™ืจื™ื ืฉืžื’ื“ืœื™ื ืฉืขืจื•ืช ืขืœ ื›ืœ ื”ื’ื•ืฃ ืฉืœื ื•,
00:56
make for especially popular living quarters.
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ืžื”ื•ื•ื™ื ืื–ื•ืจื™ ืžื—ื™ื” ืคื•ืคื•ืœืจื™ื™ื ื‘ืžื™ื•ื—ื“.
00:59
Malassezia are fond of these hideouts because they contain glands
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ืžืœืกื–ื™ื” ืื•ื”ื‘ื™ื ืืช ื”ืžื—ื‘ื•ื ื”ื–ื” ื‘ื’ืœืœ ืฉื”ื ืžื›ื™ืœื™ื ื‘ืœื•ื˜ื•ืช
01:03
that secrete an oil called sebum
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ืฉืžืคืจื™ืฉื•ืช ืฉืžืŸ ืฉื ืงืจื ืกื‘ื•ื
01:06
thatโ€™s thought to lubricate and strengthen our hair.
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ืฉื ื—ืฉื‘ ื›ืžืฉืžืŸ ื•ืžื—ื–ืง ืœืฉื™ืขืจ ืฉืœื ื•.
01:09
Malassezia evolved to consume our skinโ€™s proteins and oils.
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ืžืœืกื–ื™ื” ื”ืชืคืชื—ื” ืœืฆืจื•ืš ืืช ื”ื—ืœื‘ื•ื ื™ื ื•ื”ืฉืžื ื™ื ืฉืœ ื”ืขื•ืจ ืฉืœื ื•.
01:15
And because of its many sebum-secreting follicles,
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ื•ื‘ื’ืœืœ ื”ื–ืงื™ืงื™ื ืžืคืจื™ืฉื™ ื”ืกื‘ื•ื ื”ืžืจื•ื‘ื™ื ืฉืœื•,
01:18
our scalp is one of the oiliest places on our bodyโ€”
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ื”ืงืจืงืจืคืช ืฉืœื ื• ื”ื™ื ืื—ื“ ื”ืžืงื•ืžื•ืช ื”ื›ื™ ืฉืžื ื™ื ื‘ื’ื•ืฃ ืฉืœื ื• --
01:22
and consequently, one of the yeastiest.
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ื•ื›ืชื•ืฆืื”, ืื—ื“ ืžื”ื›ื™ ืžืœืื™ื ื‘ืฉืžืจื™ื.
01:25
As these fungi feast on our scalpโ€™s oils, dandruff may form.
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ื•ื›ืฉื”ืคื˜ืจื™ื•ืช ื”ืืœื• ืกื•ืขื“ื•ืช ืขืœ ืฉืžื ื™ ื”ืงืจืงืคืช ืฉืœื ื•, ืงืฉืงืฉื™ื ื™ื›ื•ืœื™ื ืœื”ื•ื•ืฆืจ.
01:30
This is because sebum is composed of both saturated and unsaturated fatty acids.
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ื–ื” ื‘ื’ืœืœ ืฉืกื‘ื•ื ืžื•ืจื›ื‘ ื’ื ืžืฉื•ืžื ื™ื ืจื•ื•ื™ื™ื ื•ื’ื ืœื ืจื•ื•ื™ื™ื.
01:36
Saturated fats neatly pack together.
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ืฉื•ืžื ื™ื ืจื•ื•ื™ื™ื ืืจื•ื–ื™ื ื‘ืฆื•ืจื” ื™ืคื” ื™ื—ื“.
01:39
Unsaturated fats, on the other hand,
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ืฉื•ืžื ื™ื ืœื ืจื•ื•ื™ื™ื, ืžืฆื“ ืฉื ื™,
01:41
contain double bonds that create an irregular kink in their structure.
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ืžื›ื™ืœื™ื ืงืฉืจื™ื ื›ืคื•ืœื™ื ืฉื™ื•ืฆืจื™ื ืงืžื˜ื™ื ืœื ืจื’ื™ืœื™ื ื‘ืžื‘ื ื” ืฉืœื”ื.
01:46
Malassezia eat sebum by secreting an enzyme
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ืžืœืกื–ื™ื” ืื•ื›ืœื™ื ืกื‘ื•ื ืขืœ ื™ื“ื™ ื”ืคืจืฉืช ืื ื–ื™ื
01:50
that releases all of the oilโ€™s fatty acids.
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ืฉืžืฉื—ืจืจ ืืช ื›ืœ ื”ื—ื•ืžืฆื•ืช ื”ืฉื•ืžื ื™ื•ืช ืฉืœ ื”ืฉืžืŸ.
01:53
But they only consume the saturated fats, leaving the unsaturated ones behind.
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ืื‘ืœ ื”ื ืจืง ืฆื•ืจื›ื™ื ืืช ื”ืฉื•ืžื ื™ื ื”ืจื•ื•ื™ื™ื, ื•ืžืฉืื™ืจื™ื ืžืื—ื•ืจ ืืช ื”ืœื ืจื•ื•ื™ื™ื.
02:00
These irregularly shaped leftovers soak into the skin
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ื”ืฉืืจื™ื•ืช ื‘ืฆื•ืจื•ืช ื”ืœื ืจื’ื™ืœื•ืช ื ืกืคื’ื•ืช ืœืชื•ืš ื”ืขื•ืจ ื•ืคื•ืจืฆื•ืช ืืช ื”ืžื—ืกื•ื ืฉืœื•,
02:05
and pry its barrier open, allowing water to escape.
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ืžื” ืฉืžืืคืฉืจ ืœืžื™ื ืœื‘ืจื•ื—.
02:10
The body detects these breaches and responds defensively,
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ื”ื’ื•ืฃ ืžื–ื”ื” ืืช ื”ืคืจื™ืฆื•ืช ื”ืืœื• ื•ืžื’ื™ื‘ ื”ื’ื ืชื™ืช,
02:14
causing the inflammation that gives dandruff itโ€™s itch.
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ืžื” ืฉื’ื•ืจื ืœื”ื“ืœืงื” ืฉื ื•ืชื ืช ืœืงืฉืงืฉื™ื ืืช ื”ื’ืจื•ื“ ืฉืœื”ื.
02:18
It also makes the skin cells proliferate to repair the damaged barrier.
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ื”ื™ื ื’ื ืžืืคืฉืจืช ืœืชืื™ ืขื•ืจ ืœืฉื’ืฉื’ ื›ื“ื™ ืœืชืงืŸ ืืช ื”ืžื—ืกื•ื ื”ืคื’ื•ื.
02:24
Usually, our skinโ€™s outer surface, or epidermis,
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ื‘ื“ืจืš ื›ืœืœ, ืฉื˜ื— ื”ืคื ื™ื ื”ื—ื™ืฆื•ื ื™ ืฉืœ ื”ืขื•ืจ ืฉืœื ื•, ืื• ืืคื™ื“ืจืžื™ืก,
02:27
completely renews itself every two to three weeks,
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ืžืชื—ื“ืฉ ืœื’ืžืจื™ ื›ืœ ืฉื ื™ื™ื ืขื“ ืฉืœื•ืฉื” ืฉื‘ื•ืขื•ืช,
02:31
Epidermal cells divide, move outwards, die,
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ืชืื™ ืืคื™ื“ืจืžื™ืก ืžืชื—ืœืงื™ื, ื ืขื™ื ื”ื—ื•ืฆื”, ืžืชื™ื,
02:34
and form the skinโ€™s tough outer layer,
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ื•ื™ื•ืฆืจื™ื ืืช ื”ืฉื›ื‘ื” ื”ืงืฉื•ื—ื” ื”ื—ื™ืฆื•ื ื™ืช ืฉืœ ื”ืขื•ืจ,
02:37
which gradually sheds off in single cells far too small to see.
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ืฉื‘ื”ื“ืจื’ื” ืžืฉื™ืœ ื‘ืชืื™ื ื‘ื•ื“ื“ื™ื ืงื˜ื ื™ื ืžื›ื“ื™ ืœืจืื•ืช.
02:42
But with dandruff, cells churn out quickly to correct the broken barrier,
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ืื‘ืœ ืขื ืงืฉืงืฉื™ื, ืชืื™ื ื ื•ืฆืจื™ื ื‘ืžื”ื™ืจื•ืช ื›ื“ื™ ืœืชืงืŸ ืืช ื”ืžื—ืกื•ื ื”ืคื’ื•ื,
02:47
meaning they donโ€™t mature and differentiate properly.
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ืžื” ืฉืื•ืžืจ ืฉื”ื ืœื ืžืชื‘ื’ืจื™ื ื•ืžืชื—ืœืงื™ื ื‘ืฆื•ืจื” ื ื›ื•ื ื”.
02:50
Instead, they form large, greasy clumps around the hair follicle
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ื‘ืžืงื•ื, ื”ื ื™ื•ืฆืจื™ื ื’ื•ืฉื™ื ื’ื“ื•ืœื™ื ื•ืฉื•ืžื ื™ื™ื ืกื‘ื™ื‘ ื–ืงื™ืงื™ ื”ืฉื™ืขืจ
02:55
that are shed as visible flakes.
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ืฉืžื•ืฉืจื™ื ื‘ืคืชื™ืชื™ื ื ืจืื™ื.
02:58
This is how Malasseziaโ€™s voracious appetite
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ื›ืš ื”ืชืื‘ื•ืŸ ื”ืจืขื‘ืชื ื™ ืฉืœ ื”ืžืœืกื–ื™ื”
03:01
and our bodies reaction to its by-products lead to dandruff.
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ื•ื”ืชื’ื•ื‘ื” ืฉืœ ื”ื’ื•ืฃ ืฉืœื ื• ืœืชื•ืฆืจื™ ื”ืœื•ื•ืื™ ืฉืœื• ืžื•ื‘ื™ืœื™ื ืœืงืฉืงืฉื™ื.
03:06
Currently, the most effective way to get rid of dandruff
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ื›ืจื’ืข, ื”ื“ืจืš ื”ื™ืขื™ืœื” ื‘ื™ื•ืชืจ ืœื”ืคืชืจ ืžืงืฉืงืฉื™ื
03:09
is by using antifungals in things like shampoos,
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ื”ื™ื ืขืœ ื™ื“ื™ ืฉื™ืžื•ืฉ ื‘ื ื•ื’ื“ื™ ืคื˜ืจื™ื•ืช ื‘ื“ื‘ืจื™ื ื›ืžื• ืฉืžืคื•,
03:12
applied directly to the scalp, to kill Malassezia.
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ืฉืžื•ืฉืžื™ื ื™ืฉื™ืจื•ืช ืขืœ ื”ืงืจืงืคืช, ื›ื“ื™ ืœื”ืจื•ื’ ืืช ื”ืžืœืกื–ื™ื”.
03:16
For those who experience dandruff,
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ืœืืœื” ืฉื—ื•ื•ื™ื ืงืฉืงืฉื™ื,
03:18
it usually comes and goes as sebum secretions vary throughout one's lifetime
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ื–ื” ื‘ื“ืจืš ื›ืœืœ ืžื’ื™ืข ื•ื”ื•ืœืš ื›ืฉื”ืคืจืฉื•ืช ื”ืกื‘ื•ื ืžืฉืชื ื•ืช ื‘ืžื”ืœืš ื”ื—ื™ื™ื
03:22
due to hormonal changes.
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ื‘ืฉืœ ืฉื™ื ื•ื™ื™ื ื”ื•ืจืžื•ื ืœื™ื.
03:24
But despite the fact that Malassezia colonize everyone to a similar extent,
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ืื‘ืœ ืœืžืจื•ืช ื”ืขื•ื‘ื“ื” ืฉืžืœืกื–ื™ื” ืžืื›ืœืกืช ืืช ื”ืจืืฉื™ื ืฉืœ ื›ื•ืœื ื‘ืื•ืชื” ืจืžื”,
03:29
not everyone gets dandruff.
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ืœื ื›ื•ืœื ืกื•ื‘ืœื™ื ืžืงืฉืงืฉื™ื.
03:31
Some people are more susceptible.
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ื›ืžื” ืื ืฉื™ื ื™ื•ืชืจ ืจื’ื™ืฉื™ื.
03:33
Exactly why is unclear.
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ื‘ื“ื™ื•ืง ืœืžื” ื–ื” ืœื ื‘ืจื•ืจ.
03:35
Do people with dandruff have a certain genetic predisposition?
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ื”ืื ืœืื ืฉื™ื ืขื ืงืฉืงืฉื™ื ื™ืฉ ื ื˜ื™ื•ืช ื’ื ื˜ื™ื•ืช ืžืกื•ื™ื™ืžื•ืช?
03:38
Is their skin barrier more permeable?
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ื”ืื ืžื—ืกื•ื ื”ืขื•ืจ ืฉืœื”ื ื™ื•ืชืจ ื—ื“ื™ืจ?
03:41
Scientists are currently investigating if people with dandruff do, in fact,
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ืžื“ืขื ื™ื ื›ืจื’ืข ื—ื•ืงืจื™ื ืื ืื ืฉื™ื ืขื ืงืฉืงืฉื™ื, ืœืžืขืฉื”,
03:45
lose more water through their scalps,
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ืžืื‘ื“ื™ื ื™ื•ืชืจ ืžื™ื ื“ืจืš ื”ืงืจืงืคืช,
03:47
and whether this is whatโ€™s leading their skin cells to proliferate.
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ื•ื‘ื™ืŸ ืฉื–ื” ืžื” ืฉืžื•ื‘ื™ืœ ืืช ืชืื™ ื”ืขื•ืจ ืฉืœื”ื ืœืฉื’ืฉื’.
03:52
Researchers are learning that Malassezia communicate with our immune system
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ื—ื•ืงืจื™ื ืœื•ืžื“ื™ื ืฉืžืœืกื–ื™ื” ืžืชืงืฉืจืช ืขื ืžืขืจื›ืช ื”ื—ื™ืกื•ืŸ ืฉืœื ื•
03:56
using small, oily molecules called oxylipins that regulate inflammation.
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ื‘ืฉื™ืžื•ืฉ ื‘ืžื•ืœืงื•ืœื•ืช ืฉื•ืžื ื™ื•ืช ืงื˜ื ื•ืช ื‘ืฉื ืื•ืงืกื™ืœื™ืคื™ื ื™ื ืฉืžื ื˜ืจื™ื ืืช ื”ื”ื“ืœืงื”.
04:02
If they can find a way to inhibit inflammatory oxylipins
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ืื ื”ื ื™ื•ื›ืœื• ืœ ืžืฆื•ื ื“ืจืš ืœื”ืฉื‘ื™ืช ืืช ื”ืื•ืงืกื™ืœื™ืคื™ื ื™ื ื”ื“ืœืงืชื™ื™ื
04:06
and boost anti-inflammatory ones, they could develop new treatments.
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ื•ืœื”ื’ื‘ื™ืจ ืืช ืืœื” ื”ืื ื˜ื™ ื“ืœืงืชื™ื™ื, ื”ื ื™ื•ื›ืœื• ืœืคืชื— ื˜ื™ืคื•ืœื™ื ื—ื“ืฉื™ื.
04:11
Scientists are also investigating if thereโ€™s any benefit to our relationship
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ืžื“ืขื ื™ื ื’ื ื—ื•ืงืจื™ื ืื ื™ืฉ ืชื•ืขืœื•ืช ืœื™ื—ืกื™ื ืฉืœื ื•
04:16
with Malassezia.
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ืขื ื”ืžืœืกื–ื™ื”.
04:17
They hypothesize that dandruff,
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ื”ื ืžืฉืขืจื™ื ืฉืงืฉืงืฉื™ื,
04:19
which can be uncomfortable and embarrassing for us,
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ืฉื™ื›ื•ืœื™ื ืœื”ื™ื•ืช ืœื ื ื•ื—ื™ื ื•ืžื‘ื™ืฉื™ื ื‘ืฉื‘ื™ืœื ื•,
04:22
creates a reliable, oily food source for the yeast.
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ื™ื•ืฆืจื™ื ืžืงื•ืจ ืื•ื›ืœ ืืžื™ืŸ ื•ืฉื•ืžื ื™ ืœืฉืžืจื™ื.
04:26
But dandruff isnโ€™t contagious or a great threat to our health.
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ืื‘ืœ ืงืฉืงืฉื™ื ืœื ืžื“ื‘ืงื™ื ืื• ืžื”ื•ื•ื™ื ืกื™ื›ื•ืŸ ืœื‘ืจื™ืื•ืช.
04:29
And Malassezia seem to excel at defending their territory, our skin,
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ื•ื ืจืื” ืฉืžืœืกื–ื™ื” ืžืฆื˜ื™ื™ื ืช ื‘ื”ื’ื ืช ื”ื˜ืจื™ื˜ื•ืจื™ื” ืฉืœื”ื, ื”ืขื•ืจ ืฉืœื ื•,
04:34
from other, more harmful microbes like Staphylococcus aureus.
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ืžื—ื™ื™ื“ืงื™ื ืžื–ื™ืงื™ื ืื—ืจื™ื ื›ืžื• ืกื˜ืคื™ืœืงื•ืงื•ืก ืื•ืจื™ืื•ืก.
04:40
So, while scientists have gotten to the bottom of many mysteries
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ืื–, ื‘ืขื•ื“ ืฉืžื“ืขื ื™ื ื”ื’ื™ืขื• ืœืคืชืจื•ืŸ ืฉืœ ื”ืจื‘ื” ืชืขืœื•ืžื•ืช
04:43
surrounding this condition, it must be said:
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ืฉืžืงื™ืคื•ืช ืืช ื”ืžืฆื‘ ื”ื–ื”, ื—ื™ื™ื‘ื™ื ืœื”ื’ื™ื“:
04:46
dandruff remains a head-scratcher.
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ืงืฉืงืฉื™ื ื ืฉืืจื™ื ื’ืจื•ื“ ื‘ืจืืฉ.
ืขืœ ืืชืจ ื–ื”

ืืชืจ ื–ื” ื™ืฆื™ื’ ื‘ืคื ื™ื›ื ืกืจื˜ื•ื ื™ YouTube ื”ืžื•ืขื™ืœื™ื ืœืœื™ืžื•ื“ ืื ื’ืœื™ืช. ืชื•ื›ืœื• ืœืจืื•ืช ืฉื™ืขื•ืจื™ ืื ื’ืœื™ืช ื”ืžื•ืขื‘ืจื™ื ืขืœ ื™ื“ื™ ืžื•ืจื™ื ืžื”ืฉื•ืจื” ื”ืจืืฉื•ื ื” ืžืจื—ื‘ื™ ื”ืขื•ืœื. ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ื”ืžื•ืฆื’ื•ืช ื‘ื›ืœ ื“ืฃ ื•ื™ื“ืื• ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ ืžืฉื. ื”ื›ืชื•ื‘ื™ื•ืช ื’ื•ืœืœื•ืช ื‘ืกื ื›ืจื•ืŸ ืขื ื”ืคืขืœืช ื”ื•ื•ื™ื“ืื•. ืื ื™ืฉ ืœืš ื”ืขืจื•ืช ืื• ื‘ืงืฉื•ืช, ืื ื ืฆื•ืจ ืื™ืชื ื• ืงืฉืจ ื‘ืืžืฆืขื•ืช ื˜ื•ืคืก ื™ืฆื™ืจืช ืงืฉืจ ื–ื”.

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