How Do I Know How Much Active to Add?

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How Do I Know How Much Active to Add?

The thinking cosmetic chemists dilemma...

You want your products to work but can't afford to test them so what do you do? The only thing you can do is look at what has been done before, look at what you have got and do a bit of calculating.

Let's take Green Tea as an example.

Scientists have been researching the link between Green Tea extract and UV protection for over twenty years looking first at how taking the extract internally (such as in tea or tablet form) influences how skin reacts to UV light and more recently looking at topical applications. The ears of the cosmetic industry pricked up in the 1990's with the publishing of several scientific studies during all concluding that applying Green Tea to the skin in one form or another before UV irradiation (sun exposure) reduced the erythema (reddening) response. In a nutshell Green Tea extract has a protective effect on the skin making it slower to become irritated and burned. It isn't hard to work out why this was so exciting!

While it is somewhat reckless to reduce the efficacy of Green Tea to one active component, there was a clear stand out in terms of the tea's chemistry that was worth special attention - EGCG or Epigallocatechin gallate.

EGCG is an antioxidant from a family of phytochemicals called catechins. This antioxidant is present in many different botanicals with the largest sources found to occur in fava beans, black grapes, apples, blackberries, raspberries and of course Green and Black Tea. Research has shown that it is the EGCG content that contributes to the positive health effects of the above super foods and what's more, the effects are just as remarkable when applied topically.

All of this is very exciting for the cosmetic brand owner, especially those based here in Australia where a combination of skin type plus intense UV radiation leaves the vast majority of the population at risk of ageing both more dramatically and faster than almost anywhere else on the planet. Sun protection in any form is essential for maintaining a youthful, vibrant look.

Collecting the Evidence.

So far we have identified an extract and an active component of that extract that leads to a positive outcome. What we must now do is find out the dose and to do that we have to evaluate the evidence. To help clear away some of the noise that comes from internet searching we recommend selecting either Google Scholar or Deep Dyvve as your search engines for your data collection needs. This will ensure that the results that are pulled up are scientific in nature rather than the usual mix of advertisement plus personal opinion that peppers Google proper. Being as though we are talking about serious anti-ageing claims - UV protection, Anti-irritation - it is important that we select sources that specialise in publishing data in this area. Dermatology, Photobiology, Biological Sciences, Pharmacology, Phytomedicine, Cosmetic Science and Herbal Medicine Journals are going to be much more relevant to you than those focusing on Nutrition, Plant Biotechnology, Farming or Cancer Research (we must remain cosmetic in our focus). Once that is sorted it is time to search.

As we are considering using green tea extract we need to search for studies looking at that, we also need to focus on studies looking at topical application rather than injection or ingestion. Studies on people using full sunlight or simulated sunlight (rather than on mice in UVB only) stand the best chance of giving us a baseline to work towards.

Working out how much to use.

We found a number of studies including this one that gave us a bit of insight into a correct dose:

"The topical application of 10% EGCG to aged human skin three times a week for 6 weeks increased the epidermal thickness. The number of Ki-67 positive keratinocytes in the basal cell layer also increased. These results indicate that the topical application of EGCG stimulates keratinocyte proliferation"

Dual Mechanisms of green tea extract (EGCG) induced cell survival in human epidermal keratinocytes.
Jin Ho Chung, Ji Hyun Han, Eun Ju Hwang, Jin Young Seo, Kwang Hyun Cho, Han Kim, Jai Il Youn and Hee Chul Eun.
Department of Dermatology, Seoul National University College of Medicine and Laboratory of Cutaneous Ageing Research, Clinical Research Institute, Seoul National University hospital, Seoul, Korea.

While the above study might not constitute a perfect study it was carried out on humans using the active that we are interested on and it did produce an effect so it seems as good a place to start as any!

So what does that work out to in % terms to add to our product?

We need to ensure that we get 10% EGCG into our product which is quite a lot really so to work out how much we should add into our cream we need to know how much EGCG is in our Green Tea Powder...

Our Green Tea Powder is 28 times stronger than the Green Tea leaves that you would drink. This is because of the way the extract has been processed (by drying to concentrate the active).The resulting powder contains between 40-50% on a weight for weight basis of the active ECGC, which is what we are after!

That means that to get 10% EGCG into our product we need to add around 21% of the green tea powder into our product! That is a lot and is probably not the kind of concentration that any cosmetic brand would be able to manage but that is what you would have to do to replicate the work done here and that is not all. A further study by Katiyar et all (1999) used a dose of 3mg/2.5cm2 skin which is a huge amount as that equates to adding 1.2mg per cm2 skin! A sunscreen is supposed to be applied at a rate of 2mg/ cm2 skin so assuming that you were to apply the green tea active based product at the same dose you would pretty much just have to add pure green tea extract to the skin as it is impossible to get that concentration from a standard powdered green tea extract. Crazy hey!

But do not despair; a further study found that just 0.2mg/cm2 (10% of applied dose) of green tea extract protected the skin from UV erythema (Green Tea and the Skin, Stephen Hsu, Department of Oral Biology and Maxillofacial Pathology, School of Dentistry, Medical College of Georgia. 2004). While this is still quite high in terms of dose, it is getting more manageable especially when you consider that we usually combine actives for a synergistic effect.

Finally another study, this time on mice suggests a dose of 50mg per week will produce positive results. As 1 gram is equal to 1000 milligrams the dose required to get a positive result was equivalent to 0.05g per week.This translates into the following dosage:

Our glycerin extract contains just under 5% Green Tea Powder and the Liquid extract contains just under 1%.

This gives us an approximate concentration of ECGC in the extracts of 2.35% in the glycerin extract and 0.47% in the liquid extract.

If you were to add the glycerin extract into a product at 10% you would end up with an active concentration of 0.235g ECGC per 100g of product. If the product were to be applied to UV exposed skin at a rate of 21g per dose you would have enough active in your product to replicate the conditions in these skin tests.

If you used 20% extract you would have to apply 10g of product to get the same result.

If you apply the neat extract to the skin (which might feel quite sticky thanks to the glycerin) you would have to apply 4.7g to the exposed skin to achieve the right amount of coverage.

To put this into perspective to apply a sunscreen properly to an average sized adults body would require 30g of product so the above is very do-able.


Tracking down evidence for your ingredients is hard, there are many green tea studies out there but some of them relate to results from taking the extract in liquid form, some as capsules, some applied green tea onto mice and some onto tissue culture (in vitro). Sometimes you have to pay for access to these papers which can also be tough as it is hard to know if that particular paper will solve your problems and give you the information you need or not before you actually get access to it.However, this is all part of the fun and if you want to make products that really work, make tall claims and create exciting headlines then you probably do need to get your head around this issue.

The good thing I've discovered about green tea from looking at all of this research is that there doesn't appear to be a maximum dose per se so if you can afford it feel free to slather it all over your body while you sit back and wait to grow younger. After all, we now have the evidence.

Happy formulating and remember that every little thing in your formula can help so if you only want a dash of green tea it may only give you a dash of benefit but that's a whole lot better than nothing!

Amanda Foxon-Hill

15 December 2014

More about: Actives, Cosmetics

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