How Do We Know Something Is Good At Moisturising?

how do we know something is good at moisturising

I was listening to the perky pair of Randy and Perry over on the Beauty Brains the other day. They were answering a question about whether or not lanolin was a good moisturiser. They replied that it was indeed but that mineral oil was better. I knew straight away why they had said that and what they were was true enough in as far as it went, but nonetheless I think they were wrong to suggest that mineral oil is actually better. But it is going to be involved to explain why, so maybe get a sandwich.

The way things like lanolin, mineral oil and vegetable oils have a moisturising effect is by forming a layer on the surface of the skin that holds the moisture in. It isn’t so very different to wrapping your skin in cling film.

The precise nature of the film that the oil produces determine how good it is at moisturising. There are a number of ways in which this effect can be measured. For example you can apply to some oil to the skin and measure the moisture content by passing a small electric current through the skin. Moist skin is more conductive to electricity so the greater the conductivity the more powerful the moisturising effect your oil has. This is a reasonable model in as far as it goes.

But it is open to some objections. For a start the conductivity might be affected directly by the oil itself. And if you are testing the oil as a component of a cream there is every chance that the other components will affect the conductivity.

Another method is simply to put a film across a container with water in it and then apply a layer of the oil to the film. You can get films that are synthetic versions of skin. There is no reason this shouldn’t give an idea of how well an oil works, but I have done this kind of experiment myself and the practice difficulties are, well, difficult.

These two methods are the most direct, but there are other ways where you track what are assumed to be the beneficial effects of moisturisation, such as how elastic the skin is or how smooth it is on the surface.

But while these techniques have their uses, none of them are totally satisfactory. The skin is a complex organ.  You can tell a certain amount about what a wine tastes like by analysing how much sugar and tannin it contains, but you don’t really get either the whole picture.  It is a bit like that measuring the effect of something applied to the skin. The numbers you get from the instrument are an indication, but the actual experience is rather more involved.

So to my mind the only way you can really tell whether or not something is moisturising is to try it out on your own skin over a period of time.  This can’t generate the kind of data you can publish in a scientific paper.  But it is a better guide to coming up with good products.  So is mineral oil the best moisturiser?  It is certainly a good one, but I wouldn’t say it was hugely better than vegetable oils.  But on my skin the star moisturiser is lanolin.  It is a bit smelly and it is difficult to rub into the skin.  It also leaves the finger you have used to apply it unusable for any other purpose for a few minutes after you have applied it.  But for moisturising effect it is great.  You notice it more quickly than with other products and the effect lasts longer.

That is my feeling anyway.  Lanolin has been out of fashion for a very long time now and it still appears on lists of things that companies choose to avoid.  And as the Brains boys say, mineral oil scores higher in reported moisturising power.  I think we are all missing a trick, but I can’t prove it.

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8 thoughts on “How Do We Know Something Is Good At Moisturising?

  1. Anita

    Very interesting, I always wondered how these things were tested.
    Also curious to know why lanolin isn’t in fashion. One of my favourite lip products (Lanolips) contains lanolin and it works a lot better than any other lip moisturising products I’ve tried.

  2. K

    But does moisturising mean to introduce more water into the skin or to help the skin to retain water?

  3. Andrea

    Lanolin also works best for me

    I used to be able to get a private label lotion called Lanphilic that did wonders for my feet but it’s been gone for a couple years.

    I’ve been using Shea butter based lotions instead which seem to work okay.

    If my feet need real attention I will use the lanolin anhydrous and put socks on overnight but it just feels so greasy I don’t like to use it on a regular basis.

  4. Colin Post author

    @K moisturisation works by helping the skin to retain moisture.

    @Perry, on my skin lanolin has a longer lasting effect but both are pretty good. Petrolatum is a better bet for people with sensitive skins in theory, as less natural ingredients tend to provoke fewer allergies. But I don’t have any experience or data to back that hunch up.

  5. Pedro

    Lanolin works extremely well on my lips (they are prone to severe dryness). But petrolatum doesn t work well for them at all (seems to last just about 30min).

  6. Cheryl

    I am with you on this one! The scientist in me will accept that in our ‘scientific test’s’ Mineral oil is a front runner for reducing TEWL, but the formulator and ingredient junkie in me will say, mineral oil does nothing apart from ‘film form’ whereas other ingredients have a mixture of film forming properties along with vitamins and antioxidants. Those other bits n bobs, while they won’t show an instant decrease in TEWL are likely to be active in improving the skins long term health and water retention abilities! That is my opinion anyhow 🙂

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