Cosmetic Preservatives – the Good, the Bad and the Ugly

A couple of weeks back I had an exchange of comments with a fellow blogger about preservatives. She was optimistic that developments in science will soon produce safer preservatives for the cosmetic industry. This started me thinking about preserving methods currently in use and where new developments may come from.

There are three broad methods of preservation in use by the cosmetic industry today:

1.      Going water free

This is the most straightforward preservation method – where there is no water there is no life. Simple.

This is how granny used to make her ointments. Today we are benefiting from a much wider choice of vegetal oils and butters than granny ever had, so it is possible to make combinations that feel lighter and quicker to absorb into the skin.

There is no guarantee that a water-free product will be also free from preservatives. Some manufacturers add preservatives anyway, in case the product gets mixed with water during use. But if you check the labels you will be able to find oils, balms and ointments with no added preservatives.

Over the last few years, consumers have been gradually getting more used to water-free, oil-based cleansers and moisturisers and it possible these products may continue to increase in popularity.

2.     Preserving with substances that kill microbes (biocides)

Biocides started to be used in the 1930s. They are what people usually mean these days by ’preservatives’. The cosmetic industry has been heavily relaying on them for keeping water-based cosmetics free from microorganisms.

The perfect biocide – effective against all microbes and devoid of irritant or sensitizing potential – is still to be found. And it is a mighty challenge. Why? Because microbes are very tough and adptable little organisms. They have been around for a lot longer than us humans and they may well continue to thrive on this planet long after we are gone. Some people would even say we humans are here because the microorganisms let us. There are plenty of substances harmful to us but congenial to at least some microbes. Finding something that works the other way round will be nothing less than a strike of genius.

People with strong, healthy skin can get away with small amounts of biocides in their cosmetics. Our skin is a barrier organ and it will protect us from these substances. Are they good for the skin? We can certainly agree on one point – it is better to have preservatives in cosmetics than being exposed to the host of bacteria, moulds and fungi ready to take over an unpreserved water-based product.

Scientists are indeed on the look out for better biocides. The one recent development I find most interesting in this area is antimicrobial peptides. They are natural mechanisms deployed by living organisms against microbial invaders. With genetic engineering, it would be possible to make them effective against a broad spectrum of microbes. There is a serious caveat – bacteria evolve to become resistant to antimicrobial peptides. If we start using peptides on a wide scale, as drugs and preservatives, bacteria will up their game too. They will develop resistance faster. And not only to our drugs and preservatives, but also - crucially and dangerously – to the antimicrobial peptides our own bodies naturally use to fight infections. We might be in for a lot more than we have bargained for.

3.     Making the water in cosmetics unavailable to micro-organisms

This is a method humankind has used from time immemorial to preserve food – salting, pickling and sweet preserves (in honey and more recently sugar). The reason why these substances works as preservatives is because they bind water so strongly that it becomes unavailable to microorganisms.

Over the last few years cosmetic formulators have started to experiment with water binding substances – glycerin, sugar and even salt – as preservatives. There is one major difficulty, in that large amounts of these substances are necessary to bind all the water in a product. Which will make the product feel sticky (like jam) or drying to the skin (too much salt). So this preserving method is more useful for reducing the amount of biocides (preservatives of the killing type) in a product than replacing them altogether.

Three different approaches to giving cosmetics a shelf life – three sources of inspiration for the cosmetic scientists of the future. Which one is going to give us the lasting new trend? If you were a betting person which one would you put your money on?

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