Eye cream, face cream, body cream and feet. Why one size doesn’t always fit all.

Skin is skin isn’t it?

If you are trying to down-size your bathroom cabinet in an attempt to shrink your carbon footprint or save money seeing the skin as all the same is a reasonable place to start.   The one-skin-one-moisturiser approach.  I did that for the year that I went backpacking out into the wilds of Indonesia and across Australia.  I took my first ‘home made’ cream (an aqueous cream base infused with lavender and tea tree essential oil that I’d mixed in) and that was all I used except for the occasional dab of sunscreen – I really wasn’t that sun aware back then and neither was I in need of an eye or foot cream, I was only 20 and was only interested in keeping my spots and the mozzy bites at bay.

So is it fair to say that the skin is all the same and this approach is enough for everyone or are we missing something?

Well yes, one could say that to a point.  The 20 year old me had a very short and non-specific criteria for the moisturiser and I started off with a base that was pretty bland – not too heavy or greasy. It isn’t always like that.

A better approach for a cosmetic chemist to take is to think holistically about where the product is to be applied, how often and for what purpose.

Let’s consider the eye area.

Now I’m in my 40’s I find my eyes get dry and itchy more often so an eye cream certainly feels like something I need after rubbing them one-and-off all day (I have allergies).  While the skin that my product will be applied to (the stratum corneum) is the same as the skin that I can find on my back it is fair to say that it is nowhere near as robust and this is highly relevant.

The stratum corneum is layer of cells that we present to the world. These are essentially dead cells that act as our first line of defence against outside intruders.  The stratum corneum around our eyes is the thinnest skin that cosmetic chemists have to work with and that is worth taking into consideration.  Because the S.C is so thin around the eyes it is reasonable to expect this skin to be more sensitive than skin on say your back or your feet. Indeed, as an aside, one of the biggest practical faults in using animal models as human dermatology reference points is the huge variation in Stratum Corneum thickness.  In some cases it is like comparing someone wearing a suit of amour with someone in a silk nighty! The cosmetic chemist should take into consideration the reality that of all the skin you could apply a cosmetic to, this is quite probably the most sensitive area and formulate accordingly.

But it is not just the potential for irritation that is important.  This delicate area doesn’t benefit from being tugged at or rubbed hard so it is important that us cosmetic chemists appreciate that and design products that either sink in quickly or that can be spread lightly.  What we are talking about here is rheology or flow.  It isn’t always the case that a moisturiser should sink in quickly,  for people with very dry skin or for products that benefit from being massaged or from remaining towards the surface of the skin (like sunscreens and make-up) a long-flow is more appropriate.  However, around the eyes it is best that a product sink into the skin quickly with minimal rubbing (shear force).  Another angle in this pot of considerations is to do with the products ability to wet the surface (surface tension modification).  Think of how water droplets form a bead on the skin versus oils that seem to spread out very easily.  I try to formulate products for the eye area that have a higher tendency to bead than spread far and wide so they don’t spread out INTO the eye its self (and sting).  The balance between spreadability and difficult-to-rub in is achieved by careful selection of emulsifier (if required), oil phase ingredients and percentage and composition of the water phase.  See, there is quite a bit to think about!

A pretty obvious eye area consideration is aroma.  Not many people want their eye area to be highly perfumed, indeed there is no need for it.  An eye product may be unscented, use scent just to cover the base formula aroma or may use aroma as part of its actives (cucumber carrier oil or essential oils for example).  What is important here is that the perfuming agents are chosen for their low risk of sensitivity and solar reactivity (non photosensitising).  If using essential oils it is also important to look at whether they will enhance the overall skin penetration of the formula or not (some EO’s are penetration enhancing and thus may increase the likelihood of the formula being irritating).  When aroma is used intentionally it is usually kept to a low level – typically half to a quarter of that used in a regular facial moisturiser.

Another angle to consider is efficacy (what the product is to achieve). When it comes to the eye area the big issue is dark circles!

What causes dark circles to form under the eyes is surprisingly complex and an easy-to-read paper explaining this can be found here: What causes dark circles under the eyes? Journal of Cosmetic Dermatology, Volume 6 (3) – September 1, 2007. 

In a nutshell (and for those who haven’t got time to read the attachment), eye bags have a variety of causes from allergy to trauma (swelling) to  fatty deposits and circulatory issues to increased melanin deposition to general fatigue.  One assumes, as a cosmetic chemist that one is creating a product for a ‘cosmetic-only’ application rather than a pathological diseased state.  So, we mostly focus on the visible and topically correctable issues and work there.  It might be totally appropriate to have a brightening eye cream with ingredients that suppress melanin production somewhat if your eye discolouration has a melanin factor to it.  It is unlikely that the eyes would then become white while the rest of the facial skin remained your natural colour because you are starting off with more melanin that necessary in the target area – the aim would be to shade it down to match the bulk of your facial skin.  If the problem is oedema (swelling) a low-irritant formula containing a topical anti-inflammatory active that is cosmetically acceptable, such as bisabolol might be appropriate.  If the problem is fatty circulatory it might be possible to try adding some mild vasodilating herbal extracts to the formula – not too much though as opening up the microcirculation too far might lead to more blood pooling rather than less.

To sum up, without even having to go to the extent of reading paper after paper after paper, we can already see that the eye area has its own specific set of ‘problems’,  it’s own considerations when it comes to wearability and practicality and it’s own way of best applying it.  We haven’t even looked at the business case yet  – the fact that the products are usually used in small amounts (small surface area of the body to apply to) so can retail for a much higher price per ml than most body creams that have a higher dosage requirement.  This premium price point does open the product up for the addition of the very best of anti-ageing actives, much more so than can be afforded in general skin care.

And what about the rest of the body?

While it is fair to say the eye area has the most intricate set of requirements for the cosmetic chemist to work around, the eye area is not the only place on the body that can benefit from special treatment.   Foot and hand products benefit from being non-greasy or slippery, should sink in relatively quickly but feel quite nourishing, heavy even (in some cases). Perfume wise, these ares can often tolerate quite a bit more aroma than products for other areas of the body but that does change when the audience has a chronic dry and cracked skin condition.   Hands and feet are very similar but the chemist should keep in mind that hands are exposed to far more sun (usually) and weather extremes than feet, that feet are more often occluded (covered and prone to sweating) in socks and shoes than hands (which are generally out or in gloves) and that hands are more often immersed in surfactants than feet (hand wash, dish washing etc).   Body products may benefit from being extra shiny and slippery,  may be more attractive to customers if they have a more potent and attractive aroma but need to be cheaper due to the higher use level.  Also as a body product is designed to be applied all over the body, the allergenic or irritant potential of the formula should be taken into consideration  – the bigger the dose, the more likely a reaction.

So one size doesn’t really fit all then?

To this I’d say yes and no.

If you have skin that is behaving its self, giving you little to be concerned about, then a basic light moisturising cream just to help the natural barrier functioning out when it is a bit stressed (too much swimming, hot or cold weather, too little sleep etc) may well be more than enough to keep you happy. But if this isn’t you and especially if you have specific concerns about an area of your skin then I’d personally seek out a product formulated with that area and your specific issue in mind, especially if you are looking to spend a decent amount of  money on trying to ‘correct’ whatever it is.

The bottom line is that it is a cosmetic chemists job to produce an applied solution to a specific concern (real or perceived) and that involves them looking at more than just the morphology of the skin.