A lot of the appeal of high end skin care is that it contains active ingredients that do good things for you. It’s a nice thought, but it is as well to be aware that getting through the skin is no mean feat for a molecule. The top layer of the skin is like a sponge, but one that holds onto stuff. And it is also continually being shed – so stuff that gets onto your skin doesn’t stay there too long. And on top of that there is a continual flux of water from inside your body escaping outwards – known as the trans epidermal water loss.
So if you want to get an effect by applying something to the skin you have the odds stacked against you. Nonetheless there are transdermal patches and skin creams that can be shown to be effective, but they are a select group. Nicotine patches for example can deliver enough nicotine into the blood stream to have significant effects. A friend of mine was on a clinical trial for nicotine patches and found that they induced really lurid dreams. In the end she had to go back on the fags to get off the patches.
Nicotine has just the right kind of chemistry to make it an effective skin penetrator. Another similar molecule is caffeine. This has been being used in skin penetration work as a model drug for ages and there are loads of papers published that show how well it does it. The metabolic effects of caffeine are well known to all of us – lots of us absolutely rely on them to get us up in the morning.
An intriguing possibility is that given that caffeine can cross the skin, and that it can stimulate the metabolism, can it give a local boost to fat burning? This is the idea behind what are often called body sculpting products. You can use them to loose weight just where you need to lose it.
This is a fantastic promise – a way of changing the shape of of fat deposits simply by applying a cream to the places they are too large. A lot of us would buy that. And in principle it ought to work. The trouble is that caffeine is a very small very soluble molecule so the chances are the blood stream will simply carry it away and dilute it before it can take effect. Sadly I have yet to see a credible study that shows caffeine working to actually sculpt the body. But I live in hope that one day the technical problems will be overcome somehow.
But there is one paper in the literature that shows a rather more unexpected effect of caffeine. Caffeine was applied to the skin and the rate of trans epidermal water loss. This had no effect on women, but it decreased the rate water was lost from male skin.
This is a fascinating and to me at least surprising result. For a start it shows caffeine applied topically having a physiological effect in a local area. It isn’t the right effect or the right area of action to justify the body sculpting idea, but even so it is a pointer that maybe it isn’t impossible even if we haven’t yet achieved it.
It is also interesting that the skin’s barrier function can be modified in this way. A product that only works on men and doesn’t have that big an effect anyway isn’t in itself all that exciting. But if the authors are right it suggests that the skin’s ability to retain water might be under hormonal control. As we all suffer from drier skin as we get older, maybe there will be some way of slowing that effect down.