Tuesday, February 3, 2015

Debate: Water soluble or oil soluble preservatives in a scrub

There is quite a lively debate ongoing in the bath & body community about what kind of preservatives to use in an oil or emulsified scrub. (Heck, there's a debate about whether we need to use a preservative in a scrub, but I'm firmly on the side of "yes" for that one!) The question is this - do we use a water soluble or an oil soluble preservative in the product?

A scrub - emulsified or not - is an anhydrous or non-water containing product. We don't normally preserve anhydrous products as beasties need water to grow. A scrub, however, will come into contact with water as we dip our hands into it when in the shower or at the sink - no matter how much you think you've dried your hands, you'll still have some beading down your arm when you're in the tub! - so it needs a preservative to prevent anything in the water from contaminating the product. Which kind of preservative? It's an anhydrous product, so we would need an oil soluble preservative so it'll mix in, but the water that is introduced into the product is water soluble, so we would need something water soluble.

Here's the argument from the Making Skincare Facebook page (which I copied from a public forum):
If water may be introduced to the product or the product used in a humid bathroom then a preservative is advisable. An expert microbiologist advises that if trying to preserve an anhydrous product (including all oil+sugar/salt scrub) the oil soluble preservative will get locked in the oils so will not reach any water, if water was introduced into the product. So if you added an oil soluble preservative then that preservative will stay in the oils and not move over to where the water is located to protect that water against bacteria and mould so would be useless. So contrary to what you may have read, we should really use a water soluble preservative in an anhydrous product which means we’d need to add an emulsifier to get that preservative mixed in properly with the oils.
What does this argument mean to us? The argument is that we should be using a water soluble preservative with an emulsifier in an anhydrous scrub to ensure the preservative is not locked in the oils. I've read that the water soluble preservative should be mixed with an emulsifier to make it more available for the water that might enter the scrub.

Having said this, we are generally talking about emulsified scrubs on this blog, which means there's already an emulsifier in the mix. You wouldn't need to add another emulsifier to the mix. 

There are many arguments for and against this position. Liz on the Dish forum wrote this...
Seems possible, if concerned use a preservative blend that is water soluble and oil soluble. Or use a water soluble one and add an emulsifier. However if you have an emulsifier in the mix anyway, I don't see why an oil soluble preservative wouldn't work and even better. I mean you already have it fully soluble in the oils ready to go with the emulsifier if water is introduced, unlike the water soluble preservative as it's not soluble in the formula until water is introduced. This seems to me we'd get highly concentrated spurts of preservative instead of a homogenous mixture. Anyone else?
Phenonip is one of the standards in the industry as the go to preservative for anhydrous products, even though it's not highly water soluble it does have some water solubility. But again the question of, "Is the preservative available?"...is a good one, but we wouldn't know for sure unless we test for either type. 
My guru from the Dish forum, LabRat, suggested that for an emulsified scrub, "I would use 0.3% to 0.4% Phenonip. Phenonip contains Phenoxyethanol (and) Methylparaben (and) Ethylparaben (and) Butylparaben (and) Propylparaben (and) Isobutylparaben). All of these ingredients are soluble in oil." He repeats this suggestion again and again when asked what preservative should be used in an anhydrous or emulsified scrub. He also suggested, "I would use 0.3% to 0.4% Phenonip, LiquaPar PE or LiquaPar Optima."

So to sum it all up, when it comes to preserving scrubs, we have the following positions...
1. We don't need to preserve a salt or sugar scrub because the salt or sugar bind the water so there's no chance of contamination.
2. We need to preserve an anhydrous scrub with a water soluble preservative combined with an emulsifier so it is more available to the water when it enters the scrub when we use it.
3. We need to preserve an anhydrous scrub with an oil soluble preservative.
4. We can preserve an emulsified scrub with an oil soluble preservative because it's emulsified by the emulsifier, like Polawax or Incoquat BTMS-50.
5. We need to preserve an emulsified scrub with a water soluble preservative.

Have I changed the way I preserve my emulsified sugar scrubs? No. I've been using Phenonip, a preservative that is both oil and water soluble, for eight years, and it appears* to be working.  I've read that because of these varying levels of solubility, a paraben mix would be a good preserver of oil based scrubs, so I feel pretty happy with my choice.

*I say "appears" because I've never had any growth or visible contamination in any of my emulsified scrubs. I have not had my products challenged tested as I can't afford it, although it would be very interesting to see the results! 

I've said in the past that I wouldn't use Germaben II in a sugar scrub. Have I changed my mind? Kinda...sorta...maybe? I don't think I have, although I'm always open to learning more. The parabens we find in this preservative are less oil soluble than the combination we find in Phenonip, and I haven't seen information that says that Germaben II is a better choice than Phenonip in an emulsified scrub yet.

I've written this post to open up the debate and encourage a discussion. If you have some thoughts, please share them. If you have some links, please include them. I think this is a great topic and all opinions are welcome. (As usual, be nice!)

13 comments:

Sânziene şi Mătrăgună said...

oh, indeed a thread I want to watch :)

I don't do scrubs, so I can't offer any scientific insight, so I am very curious to hear about various opinions towards water or oil soluble preservative!

thanks for an awesome debate!

Phil Geis said...

I've been in the preservative side of cosmetics for decades. The basic issue is "partitioning" - a material that likes to be in oil partitions/stays in the oil especially if it starts in the oil. Microbial growth/contamination happens in water that inadvertently comes in during use not in the oil itself. The oil is not going to donate much of that oil-loving preservative to that water - certainly not enough to prevent growth. Maybe enough that allows bugs to adapt to it.

Susan Barclay-Nichols said...

Hi Phil! I believe you're the one I'm quoting in the post!

Phil said...

Hi Susan,that's me!

Like you blog!

Lindalu said...

Hi Susan,

I do have a question on this. If we preserve the product, regardless of what preservative we use, how does it become available to the water introduced to the product? It would seem to me that like any other preservative used to lotions or creams that the preservative does not travel. For instance it does not travel with the condensation so following this logic and knowledge, how does the preservative travel from the product to introduced water?

Anonymous said...

Hi there, I've really been enjoying your website! Thank you for it :-) I've been making oil based products for a while, and just trying my hand at products containing preservatives. So if in my scrub I used oil and water and emulsified together, would the water based preservative I use also bind together with the oil and water? Many thanks. Kelly :-)

Anonymous said...

There is so much concern with the oil and water in scrubs, that no one has accounted for the scrubby parts themselves: the sugar or salt. My understanding of a chemical preservative, or any for that matter, is that for it to work fully, it has to blend with all components of the product, to effectively preserve the entire thing. How is a preservative going to protect the sugar or salt, if the preservative is bound by the 'possible' water introduction, or bound by the oil in the scrub?

Also, in relation to the need for a preservative to begin with, has the factor of actual water activity been discussed at all? The concern is to protect potential water being introduced, yet, how do you account for that when deciding proper usage rates? Or the fact that water activity may not be high enough to warrant one at all? Or are we completely banking on the fact that sugar and salt are self preserving due to their ability to bind water, which in that case would negate the need for a preservative at all?

~Christine

Kneeley said...

Hi all! This is really great timing as I've been researching different preservatives lately. I thought I'd share something I stumbled upon that is relevent to this debate. You can read the entire post here http://www.makingskincare.com/preservatives/

"PRESERVING ANHYDROUS EG SCRUBS

If water may be introduced to the product or the product used in a humid bathroom then a preservative is advisable. An expert microbiologist advises that if trying to preserve an anhydrous product (including all oil+sugar/salt scrub) the oil soluble preservative will get locked in the oils so will not reach any water, if water was introduced into the product. So if you added an oil soluble preservative then that preservative will stay in the oils and not move over to where the water is located to protect that water against bacteria and mould so would be useless. So contrary to what you may have read, we should really use a water soluble preservative in an anhydrous product which means we’d need to add an emulsifier to get that preservative mixed in properly with the oils."

Also regarding Phenonip...

"This preservative is actually unsuitable for preserving all oil products – see paragraph above entitled “Preserving Anhydrous”

Also, she mentions...

"Minimise sources of energy for microbial growth (aka “bug food”) – eg fruit, botanicals, tea, lecithin, mineral water, milk of any kind, honey, hydrosols, floral waters, aloe vera, extracts, protein, clay, powders, starches etc – reduce these to a tiny % (eg 0.1%). This is very important."

This is a little worrisome as I have quite a few proteins and oil based extracts that generally have a recommended usage of around 2-5% depending on the botanical, and I'm now a bit scared of using them :/ Does anyone have any advice on this?:(

Kneeley

La Prairie Lady said...

Hello

I make an emulsified sugar scrub with no water, just oil, staric acid, beewax and emulsifie wax, I use Optiphen Plus.

And when I add water in cream, lotion ect. I use Germall Plus.

It is wrong ??

Diane

Rachel said...

I have been making anhydrous scrubs for a long time and use Microcare or Geogard 221 with Polysorbate 80 (mixes in very easily) and have never had any problems with nasties growing in the finished scrub. I did a crude experiment ages ago with not using a preservative and allowing water into the scrub - a furry type of mould grew within 2-3 weeks.

Rania said...

Susan after your advice on the dish forum regarding using preservative in my oil/emulsified scrubs (I use 5% polysorbate 80 in all), I now use a combination of optiphen and phenonip and I haven't had an issue with a single one of my batches. I have been doing scrubs regularly for 2 years and even before switching to a combination of preservatives, I haven't had an issue while I was using phenonip alone.

Neha Kedia said...

I came across this blog yesterday. I have learned a lot from this. Recently I have started making emulsifying sugar scrub, so had some more queries.
According to me following ingredients are sufficient to make scrub
- cleansing Agent
- Emulsifiying wax
- water soluble preservative
- oil soluble preservative
- scribing agent (sugar)
- Color
- Essential oil or Fregnance

Please guide me if I am wrong

Neha Kedia said...

I came across this blog yesterday. I have learned a lot from this. Recently I have started making emulsifying sugar scrub, so had some more queries.
According to me following ingredients are sufficient to make scrub
- cleansing Agent
- Emulsifiying wax
- water soluble preservative
- oil soluble preservative
- scribing agent (sugar)
- Color
- Essential oil or Fregnance

Please guide me if I am wrong