Article by: Perry Romanowski

On a few occasions we’ve gotten a question that goes something like this….

“What is the best preservative to use?” or “What is the best ingredient I can use for moisturizing?” cosmetic-ingredients

A question like this is incredibly difficult because the answer depends on so many different factors about what you consider important.  To illustrate, let’s look a little more deeply at the question of preservatives.

What is the best preservative to use?

Preservatives are added to cosmetic formulas to prevent microbial contamination.  They are hugely important and nearly every cosmetic that is sold should have some kind of preservative.  But the best one to use will depend on a number of factors including…

  • Effectiveness
  • Formula type
  • Manufacturing conditions
  • Raw material sources
  • Cost considerations
  • Marketing considerations


Probably the most important consideration when you’re looking for the “best” ingredient.  This is the one that will best give you the effect for which you are looking.  In the area of preservatives there are many ingredients that will kill microbes.  Some work better than others and combinations typically work better than any single ingredient.  In my opinion as far as efficacy goes the best preservatives are Parabens and Formaldehyde donors.  Methylisothiazolinone blends are also quite effective.  Certainly, other ingredients work but they aren’t as broadly effective as these.  However, since other ingredients can work, effectiveness is not the only factor to consider when choosing the “best” ingredient.


While ingredients can be effective alone that doesn’t mean they will be effective in your particular formulation. Some ingredients are known to deactivate preservatives and some preservatives won’t work at certain pH levels.  Also, the oil content in your formula or the structure of your emulsion can all have an impact on whether the ingredient is effective.  Since you generally can’t know whether something will be effective just by looking at the formula on paper you have to test preservatives in your formulas.  And it makes sense to try different options.  Without giving information about the exact components of the formula, you can’t answer the question of which ingredient will work best.

Manufacturing conditions

The preservative system that you use will often depend on the manufacturing conditions under which you create your products.  Some plants are just cleaner than other plants and some facilities have tougher resident microbes than others.  I know one hair care manufacturer had to put Kathon in all their formulas because their manufacturing lines had a biofilm which was resistant to everything except Kathon.  The “best” preservative in their case was that one because it was the only thing they knew would work.

Raw Material Sources

This is similar to the manufacturing conditions but the quality of the raw materials that you are starting with will impact the decision of which is the “best” preservative to use.  If you are using ingredients from natural sources which haven’t been decontaminated from natural microbial residents you’ll have to use a stronger preservative.  If you use clean raw materials you might be able to get away with a less broadly effective preservative.

Cost Considerations

Of course you can’t figure out what the “best” ingredient is if you don’t have some sense of how much cost you are willing to absorb.  Sometimes the most effective ingredient also costs hundreds or thousands of dollars a pound and if you are selling your end product for one or two dollars you’ll never be able to afford the most effective ingredient.  In your case the “best” ingredient is the one the performs adequately within your cost constraints.  Ideally, you’ll get an ingredient that performs the way you want it to at the lowest possible cost.  For preservatives the ones that work the best also happen to be the ones that cost the least…parabens and formaldehyde donors.

Marketing Considerations

Sadly, there is a trend in which these marketing considerations get more attention than the more important factors I’ve already discussed.  But these are real considerations and sometimes you aren’t allowed to use the most effective, least expensive ingredients because your marketing position does not allow it.  If you are trying to sell a natural brand in Whole Foods you won’t be able to use parabens or formaldehyde donors.  You just can’t.  In that case the “best” preservative then becomes one of the organic acids, phenoxyethanol or other alternative, less broadly effective, and more expensive ingredients.

So, when you ask what the “best” ingredient is for your formulation remember to consider all the other factors before finding your answer.

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