Science Questions

How does hair clean itself?

Sat, 24th Jul 2010

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Ransom asked:



I have heard and read all over the place that hair cleans itself, but HOW does it do it? That's my question. I can't find it on the internet. Every time I punch in: 'how does hair clean itself?', i get all these 'how to wash your hair without shampoo', etc. but that's not my question.


So, can you tell me please, exactly HOW does hair clean itself?


Thank you


Ben -  Now thatís a good question.  I think heís probably referring to the idea that if you stop washing your hair for six weeks or so, then it ends up sort of auto-cleaning and you end up with clean hair despite it not being washed.  I think the truth is a little bit more complicated than that.  Itís not that your hair is clean; itís that your hair has the right amount of oils. 

Normally, when you wash your hair with shampoo, itís a detergent and it will strip the oils off your hair.  Hair is supposed to be a bit oily so your hair follicles produce additional oil to make up for the oil thatís been washed away and you end up getting greasy hair.  If you don't wash it away, there seems to be some kind of feedback mechanism that means that the follicles will produce the right amount of oil, and you won't end up with greasy hair.

Now I don't know if this really bears itself out in practice and from what I have seen and read about it, it seems to be much better for people with very short hair.  Itís not that they never wash their hair, itís just that they don't use soaps or shampoos Ė they just wash it with water.  The water takes away the dirt and grime but the oils stay there to help protect the hair.  Dave, you've got quite a lot of hair.  How easy is it for you to manage?

Dave -   A while ago, purely in the spirit of scientific inquiry, and much to the annoyance of my then girlfriend, I decided to see what would happen if I didnít wash my hair for three months.  Basically, what happened is my hair sort of reached an equilibrium.  It was much less greasy than it would be just before you'd wash your hair normally, but still greasier than just after it: a bit greasy, but not very greasy.  So there does seem to be some kind of feedback loop.  Also, interesting things happen when it rained because it appears that your natural grease from your hair is quite good at waterproofing because the outer layer got incredibly greasy and the rain would run off whilst the hair underneath would be entirely dry.  So obviously, natural oils have advantages over conditioners.

Ben - Thatís very strange. It's like wearing a natural shower cap made only of hair - thatís revolting.


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I reject the premise! Madidus_Scientia, Thu, 22nd Jul 2010

I dont think it does. if it did we wouldnt have to clean it would we. tangoblue, Thu, 22nd Jul 2010

Hi.... human hair is not that great at staying clean. Mainly because it's scaly so dirt gets trapped. If you stop cleaning your hair (that included brushing) it will matt up (the premise behind dreadlocks). Having said that there seems to be a trend towards no shampoo hair these days.. but they all talk about good brushing, which is effectively cleaning.

In the animal world grooming takes place. I am not comepletly aware of all the different hair/fur structures, but I do know that an Orange Utan has fine fishing wire-like hair which means that the dirt just falls off it.. no scales. JnA, Thu, 22nd Jul 2010

A barber once told my bother,

"Yur herr's like peen wire. The scissors just boonce aff."

Translating from the Scottish patois,

"Your hair is like the hardened steel wire they make pins from. My scissors can't cut it. They simply bounce off." Geezer, Thu, 22nd Jul 2010

Afaik, hair isn't self-cleaning but, like our skin, it is self-regulating with respect to the oils that are secreted to stop them from drying out and becoming dry and brittle/flaky.

The no-shampoo trend stems from the idea that removing the naturally secreted oil, by washing, just stimulates our follicles and skin to produce more oil to replace it.  If the oil is constantly removed by excessive washing the follicles and skin end up over-producing their oils in an effort to redress what they see as an imbalance.  By not using shampoo, the hair retains much of the oil secreted by the follicles, so the follicles produce less oil and your hair ends up less oily/greasy than if you keep washing it.

There have been a number of fairly well publicised tests of this 'theory' and the results do seem to bear it out.  Similarly, there have been some tests with regard to washing your body with soap and the use of antiperspirants and antideodorants, which also seem to indicate that trying to fight your body's natural regulation systems just results in overstimulating them instead.

Part of the problem is that many people don't differentiate between the oils that should be on your hair and skin, and the dirt that shouldn't.  If your hair or skin is dirty then, you should use shampoo or soap to clean it, but if your hair or skin is not actually dirty then just washing with water should suffice. LeeE, Fri, 23rd Jul 2010

So if oils get washed out of hair, whats in hair conditioner that makes it nice and supple again? FuzzyUK, Wed, 4th Aug 2010

Its almost true for your hair (after leaving your hair for over 6 weeks without washing, just plain water will be able to clean it sufficiently) but not for your body.


glorida, Mon, 16th Aug 2010

Hair is a very clever thing you see cat_with_no_eyes, Wed, 18th Aug 2010

- This thread is just superb !
Regards andrewbrak91, Mon, 23rd Aug 2010

- There have been more forums like this but this is what i loved.


Charles Charles8100, Tue, 24th Aug 2010

I dont think im going to not wash my hair for 6 weeks though :) tangoblue, Tue, 12th Oct 2010

I can attest to the waterproofing but you forgot to mention it smells like a chippan! Me, Tue, 22nd Feb 2011

Everybody talks about greasy hair .i have never had greasy hair.quite the opposite.extremely dry. What will happpen to my hair if i dont wash im hoping it will be less dry danielle vaughan, Fri, 17th Oct 2014

I haven't washed my hair with any but water, and occasionally lemon juice, for 7 years. It took about 4 months to get past the initial gross greasy phase. It's easier with long hair because you can tie it up and people don't really notice. My hair and scalp are clean and healthy with no greasy look or smell. Saves me time and $$ Mardi, Mon, 30th Mar 2015

I left my hair for 3 months without washing it and afterwards it was just an absolute greasy mess. Did not work for me Sharon adams, Sun, 20th Sep 2015

how come not washing your hair works for some and not others? Also its weird but I wake up with oily hair and sometimes in the day if Im not doing anything too much then the oil i less obvious??? Shinz, Wed, 23rd Nov 2016

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