The myth of skin washing and sebum production
Posted 18 November 2004 - 02:33 PM
From: thread (email@example.com)
Subject: Re: Too much sebum
Date: 2001-06-03 12:49:48 PST
Here is a study which discusses sebum production and the factors that affect it. I also posted a paragraph from this study which discusses the false notion of a feedback system.
Bottom-line: washing your skin does not affect sebum production one way or the other (although washing will certainly remove sebum from the skin surface).
"Sebum secretion and sebaceous lipids." - published in Dermatologic Clinics, Vol. 1, No. 3, July 1983.
Excerpt (Note: the asterisks in the excerpt represent italics in the actual paper):
"... These observations gave rise to a long-lived fallacy (1927-1957) that was posthumously christened the "feedback theory" by Kligman and Shelley (23). The idea was that sebaceous glands secrete only when necessary to replenish lipid that has been wiped or washed away. Nothing known about the physiology of sebaceous glands gives any theoretical support to this concept, and it has been thoroughly disproved experimentally (23). *Sebum is secreted continuously.* The reason that lipid levels eventually cease to increase apparently is that the skin can hold only a certain amount of lipid in its crevices, and the rest tends to flow away from sites of high sebum production (23)."
23) Kligman, A. M., and Shelley, W. B.: "An Investigation of the Biology of the Human Sebaceous Gland". Journal of Investigative Dermatology, 30:99-124, 1958.
Posted 18 November 2004 - 03:03 PM
Some of you may remember a few months ago when I went around and around with Socks over whether or not washing the skin/scalp actually stimulates the sebaceous glands to INCREASE their production of sebum. I had explained to him that Kligman et al had demolished the so-called "feedback theory" long ago with careful testing and proved that sebum is produced continuously with no regard to what's sitting on the surface of the skin/scalp, but Socks wouldn't hear of it.
Below is a posting from another site on that same issue, and my response:
>Two friends of mine had a very active sebum production. They
>washed their hair on a daily basis, because of that active
>sebum production. But one of them got tired of washing his
>hair daily and stopped doing that. Of course he had filthy
>oily hair for some weeks, but after that his scalp began to
>normalize. Now he only washes his hair once a week. I mean,
>this is just the truth.
>I'm a member of a Dutch hairloss forum and some members also
>have quit washing their hair on a daily basis with the same
I hope you'll forgive me if I find all that difficult to believe!
If you have access to a medical library, take a look at the book "Hair Research", edited by Orfanos, Montagna, and Stuttgen (copyright Springer-Verlag, Berlin Heidelberg 1981). It has a fascinating chapter titled: "Studies on the Effect of Shampoos on Scalp Lipids and Bacteria" by A. M. Kligman, K. J. McGinley, and J. J. Leydon. One of the tests they did was to have a group of volunteers completely discontinue shampooing for a full month, and then carefully measured sebum build-up on their scalps. Their sebum levels INCREASED, just as you would expect, they didn't DECREASE! Furthermore, all the subjects complained of "dirty, oily" hair. In a separate test, the same subjects shampooed their hair intensively every day for 21 days, and sebum levels on the scalp went DOWN, also just as you would expect.
BTW, if you want to read the actual study by Kligman and Shelley where they did the careful and exhaustive testing that conclusively demolished the "feedback theory", here's the full citation: "An Investigation of the Biology of the Human Sebaceous Gland", J Invest Dermatol, 30: 99-124, 1958.
Posted 19 November 2004 - 09:36 AM
Posted 22 November 2004 - 01:08 PM
Posted 22 November 2004 - 02:56 PM
EXACTLY!! People must think there are tiny little sensors of some sort sitting on the surface of the skin, and they relay information about sebum (or its absence) back to the sebaceous glands via invisible nerves, or something!
I really do recommend that people read that study by Kligman & Shelley, if they can get to a medical library. Those docs really did some thorough and ingenious testing, just to lay that theory to rest. One of the many things they did was to fix a cup tightly over the skin of test subjects, and then apply a high air pressure to the space inside. They figured, maybe it's the PRESSURE of oil and sebum on the surface of the skin that could alter the activity of the sebaceous glands underneath?? But as you can probably guess, the high air pressure on the skin had no effect at all on the measured sebum production rate. They also put a thick layer of oil (much thicker than what would normally occur) on the skin of test subjects, again with no effect on sebum production underneath.
But that does not necessarily mean washing with anything is just fine. In my own experience, any kind of soap to the face irritates the skin and produces more acne. So I use soap free skin cleansers instead. This corresponds also to what I hear other people, who should know what they talk about, say.
Exactly. Just because the "feedback theory" has been soundly disproved, that doesn't mean that you can't have some sort of allergy or contact dermatitis to something that you wash your skin with! In fact, I suspect that it's some phenomenon like that which has helped to perpetuate the "feedback theory" all these years, despite the efforts of doctors to squelch it!
Posted 22 November 2004 - 03:43 PM
I'm not here to debate the whole idea (since I really don't care) but sebum knows just like water "knows" to diffuse; it's chemical polarity. One can reason that lack of oil can induce a type of polar diffusion by way of lipids through the skin. Thought of this?
Posted 22 November 2004 - 05:19 PM
Posted 22 November 2004 - 07:52 PM
I don't think you have much of a point to make here, for the following reasons:
1) I'm not sure what you mean by "a type of...diffusion...through the skin", because it's my understanding that sebum is delivered to the skin surface exclusively by the steady emptying of lipids through the sebaceous ducts into the main duct of the pilosebaceous unit.
2) Even if you were correct about that alternate pathway of sebum delivery to the surface (diffusion through the skin itself), that still doesn't address the primary issue that the whole process is limited by the INTRINSIC PRODUCTION RATE of the sebaceous glands themselves. An increased delivery for your very hypothetical reason ("diffusing" through the skin after washing) would be very temporary.
Interestingly, an analogous situation occurs with the temporarily increased appearance of sebum due to higher ambient temperatures (1): they increase the delivery of sebum to the skin for a while apparently by reducing its viscosity, but that doesn't mean that sebum itself is being produced at a faster rate by the sebaceous glands. It will still average-out over time to that intrinsic rate.
1) "The Effect of Local Temperature Variations on the Sebum Excretion Rate", Cunliffe et al, Br J Derm (1970) 83, 650.
Posted 22 November 2004 - 07:57 PM
Again -- think of how water can defy gravity to move to dry "land"-- it means it's a polar chemical, not that it has a brain.
Posted 22 November 2004 - 08:12 PM
I wish you would be VERY cautious in your choice of your words! When you say "speed production" or "produced less", I tend to assume that you're referring to the actual production rate of sebum by the sebaceous glands, as opposed to the appearance on the skin (whatever the route it takes to get there)! Can you clarify PRECISELY what you mean above?
Posted 22 November 2004 - 08:18 PM
Posted 22 November 2004 - 08:38 PM
Posted 22 November 2004 - 11:25 PM
Posted 23 November 2004 - 04:29 PM
Uh, most definately. Many things become out of date when there are new findings.
Posted 23 November 2004 - 04:30 PM
don't let Ben ruffle your feathers too much. He always wants to be right... kind of childish if you ask me.
Posted 23 November 2004 - 06:34 PM
Excuse me, but that's obviously not the same thing as what I was referring to!
Older research gets discredited when newer research CONTRADICTS it in some way, as you correctly pointed out (more accurate experiments, newer technology, larger controlled studies, etc.). However, it doesn't get discredited just whenever some arbitrary time-limit expires!
The obvious and relevant question here is this: has Kligman and Shelley's research been contradicted, discredited, or supplanted in any way since the time it was first published in 1958?
The answer: NO. Absolutely not.
Ken's mention of the "45 years-old source" was silly and irrelevant.
Posted 23 November 2004 - 08:30 PM
Sorry for wanting to find the truth. I'll be a mindless drone like you.
As I said above, I really don't know/care to know the inner workings of sebum but just that research from 45 years ago has a way of being bad with qualitative observations because of perspective. If you find modern research that backs that, I'd be a happy camper more.
Posted 24 November 2004 - 03:18 AM
Sometimes that happens, but then sometimes old research remains spot-on! A perfect example of that would be the early seminal studies on hairloss by James Hamilton (I'm a contributor to several hairloss forums, so it's not surprising that I would also be interested in acne, a somewhat similar disorder), starting in the 1940's! And to this very day, scientific studies on hairloss still cite that early work!
If you find modern research that backs that, I'd be a happy camper more.
Instead of that, you really should take comfort in the fact that Kligman & Shelley's work is fully accepted today by doctors and scientists, with no particular need for further testing. Your objection seems to me to be an attempt to find fault just for the sake of finding fault.