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Hi everybody,
I've been trolling this forum for years but this is my first post 
While digging through mountains of scholarly research on acne, I found some evidence to suggest that P. acnes may use glycerol (aka glycerin) as a growth medium. This is particularly disturbing because glycerin is so ubiquitous in cosmetic products such as cleansers and moisturizers. While it's true that all triacylglycerides, including the lipids produced by our skin, contain a glycerol backbone, perhaps adding more glycerol from products is a bad idea. Starting today I'm going glycerin-free (luckily Dan's BP doesn't have any). I'll keep a log of progress and see if it makes a difference! Here is an excerpt that nicely summarizes the research:
From:
McGinley, K.J., Webster, G.F., Ruggieri, M.R. and Leyden, J.J. 1980. Regional variations in density of cutaneous Propionibacteria: correlation of Propionibacterium acnes populations with sebaceous secretion. Journal of Clinical Microbiology. Nov. 1980, p.672-675:
œThe correlation of P. acnes with glycerides and with products of glyceride hydrolysis suggests that glycerol or fatty acids may be important substrates for P. acnes. The in vitro demonstration that P. acnes can utilize glycerol (10) helps support this possibility, as does the finding that acne patients, who have increased levels of P. acnes along with increased sebum production, have lowered levels of skin surface glycerol than do controls or acne patients treated with antibiotics (11). The findings of increased sebum production with lower levels of glycerol when associated with higher densities of P. acnes, coupled with increasing glycerol levels as a result of antibiotic suppression of P. acnes, strongly suggests that glycerol is an important substrate for P. acnes growth.
10. Puhvel, S.M. and R.M. Reisner. 1970. Effects of fatty acids on the growth of Corynebacterium acnes in vitro. J. Invest. Dermatol. 54:48-52.
11. Rebello, T. J., and L. M. Hawk. 1978. Skin surface glycerol levels in acne vulgaris. J. Invest. Dermatol. 70:353-354.
I love research articles too! So I would like to make the following points:
1. You are citing things from the seventies. Unless this research has been followed up on within the decade it is probably not useful. It is unlikely that you have discovered something that went unnoticed by science after 1978. So, unless you can cite more recent literature, I do not think what you have given is reliable at this point in time. But it is still fun to read.
2. I would like to offer the following point for consideration: There has been a lot of recent research about what acne patients have and do not have on their skin. Prior to the last decade or so, the focus was always strongly on what we HAD on our faces that people with normal complexions don't - things like P-Acnes and excess sebum. However, a lot of recent research has focused on what we DON'T have on our faces that others do, and how this plays a role. Your article states that good-skinned people have MORE glycerol - they are only assuming that it is because the P acnes is using it, or more importantly I think, that ONLY the P acnes is using it.
But if the skin naturally has quite a bit of glycerol around, maybe it is useful for a few things. Certain fatty acids and other substances are found in much greater quantities on the faces of those who do not have acne. One that has undergone more research lately is linoleic acid. These things help our skin to fight off infections and heal properly. So, theoretically, we should consider putting more of these things on our faces instead of less. We try so hard to kill everything, that we kill the good stuff too and make our faces go nuts. It's like the fight to control oiliness - the more oil we remove from our faces, the more sebum we produce. Sebum is ironocally comedogenic because it is mostly made up of oleic acid, and very little linoleic acid. Oleic acid is comedogenic, so drying out your face causes it to naturally produce a highly comedogenic substance. Here's a fun fact you may already know - applying human sebum to bunny ears gives them zits. Trying to get rid of the acids and oils and glycerols takes away everything your skin has to fight infection and rebuild itself.
So I am questioning your hypothesis and continuing to smear glycerin on my face for the time being.
Now, I have not studied glycerol much, because most of what I have heard is not conclusively bad. I think the fact that people with good skin have more of it should not make you want to ban it. Why are those people's skins not feeding the P acnes with it? Not because they have less, the study says so itself. There is no logic in getting rid of glycerol if the body is naturally producing it quite happily in good-skinned people. You are not going to starve out the P acnes - that's just not how it works. The only dilemma for me is the part about P acnes growing from it in vitro. Now that's some gross. BUT, once again I would argue that our faces are full of good and bad bacteria, and it is almost impossible to feed some and not others. So you are left with the option of starving them all, which I suspect is a big part of the cycle of acne.
Thanks for writing this as it is always nice to know there are other researchers out there.
Let me know if you find any more recent data about this.