I’ve Learned This as a Cosmetic Formulator: Why Phenoxyethanol Alone May Not Be Enough

By the founder of Remih Skincare | Cosmetic Formulator Since 2015

When I started formulating skincare, one of the lessons I quickly came to appreciate was that making a beautiful product and making a safe product are two very different things.

A lotion can have a luxurious texture. A serum can feel silky on the skin. A toner can smell fresh and look perfectly clear.

But none of these qualities tells you whether the product is adequately protected against microbial contamination.

And this is where I want to have an important conversation with fellow skincare formulators, especially those making their own products at home or starting a cosmetic brand.

Having a preservative in your formula does not automatically mean your product is adequately preserved.

Let me explain.

The preservative mistake I want every formulator to understand

Over the years, as I have continued learning about cosmetic ingredients and developing skincare formulations, I have come to appreciate just how much thought must go into protecting a water-based product.

One ingredient that frequently comes up in these conversations is phenoxyethanol.

It is a widely used cosmetic preservative, and for good reason. It provides useful antimicrobial protection and is permitted in EU cosmetics at concentrations of up to 1%.

However, there is an important distinction that every formulator needs to understand.

Phenoxyethanol is a useful preservative. It is not a guarantee that every formula containing it will be adequately protected.

Why?

Because a cosmetic formula is a system. The ingredients interact, the pH matters, the packaging matters, and the microorganisms we need to control matter.

A preservative that performs well in one lotion may not provide sufficient protection in another formula.

This is why I never want formulators to approach preservation by simply adding an ingredient because they have seen it used in another product.

Understanding why an ingredient is used is just as important as knowing its name.

Why water changes everything

Imagine you have formulated a beautiful facial toner using water, glycerin and botanical extracts.

You have carefully selected your ingredients, achieved the texture you wanted and adjusted the pH.

You add phenoxyethanol, package the toner and prepare to sell it.

Everything looks right.

But here is the question: how do you know your preservation system can control the microorganisms that may contaminate that toner during manufacturing, storage or everyday use?

You cannot answer that question by looking at the product.

Water-containing cosmetics can support microbial growth when the formulation and manufacturing conditions allow it. Some contamination may not produce an obvious change in colour, smell or texture.

This is precisely why cosmetic formulation requires more than a good recipe.

It requires a scientific approach to product safety.

So, what would I consider adding?

When evaluating a water-based formula, I would not immediately reach for another ingredient without first understanding the existing preservation system.

I would consider three important areas.

1. A compatible preservative blend

Depending on the formulation, a commercial preservative system containing phenoxyethanol and ethylhexylglycerin may provide broader or improved antimicrobial performance compared with phenoxyethanol alone.

Ethylhexylglycerin can act as a preservative booster in suitable formulations.

However, this does not mean every blend will work in every product. I would check the supplier's recommended use level, pH range, compatibility and supporting technical data before making a decision.

The objective is to select a system that works in the actual formula, not simply to combine ingredients and hope for the best.

2. A suitable chelating agent

This is another area worth understanding.

Ingredients such as disodium EDTA can bind certain metal ions that may interfere with the performance of a preservation system.

Sodium phytate is another option in suitable formulations.

A chelator can support preservation, but it is not a preservative on its own. Adding it does not automatically make a product microbiologically safe.

This distinction matters because I often see formulation discussions focus on individual ingredients without considering the role each one plays in the complete system.

3. The right pH and formulation conditions

Not every preservative works equally well at every pH.

Some preservation systems have a broad effective pH range, while others depend on a more acidic environment.

This is particularly important when working with organic-acid-based preservatives.

Before selecting a preservative, I would check whether the product's pH falls within the supplier's recommended range and whether that pH remains suitable throughout the product's intended shelf life.

And remember: adjusting the pH with citric acid does not replace a preservative.

Every ingredient must have a clear purpose in the formula.

The part I would never skip: testing

If there is one principle I want emerging cosmetic formulators to take seriously, it is this:

You cannot establish the effectiveness of a preservation system simply by looking at your finished product. You need appropriate testing.

A product can look perfectly normal and still have a microbial problem.

Two important considerations are microbiological quality testing and preservative efficacy testing, also known as challenge testing.

Challenge testing evaluates how effectively the preservation system controls specified microorganisms introduced into the product under controlled conditions. ISO 11930 provides a recognised framework for evaluating the antimicrobial protection of cosmetics.

Testing helps establish whether the preservation system is appropriate for the finished formulation. It should be considered alongside good manufacturing practices, suitable packaging, stability assessment and the product's overall safety evaluation.

For a cosmetic brand, this is not an area where I would encourage shortcuts.

Your customer is trusting you with something they apply to their skin. That trust deserves more than a formula that simply looks good.

My advice to anyone building a skincare brand

If you are formulating your own skincare products, I want you to move beyond asking:

Which preservative should I buy?

Start asking better questions.

• Is this preservative suitable for my specific formula?

• Does it work within my product's pH range?

• Do my ingredients affect its performance?

• Is a chelator appropriate for this formulation?

• Has the finished product undergone the necessary preservation and microbiological testing?

• Can I support my product's safety and quality claims with evidence?

These are the questions that help you develop a more rigorous approach to formulation.

You do not need the longest ingredient list to make a good product. You need to understand the ingredients you use, select them for the right reasons and verify that your finished product performs as intended.

Why I care about getting the science right

My work in skincare formulation has taught me to look beyond what a product promises on the label.

I believe effective skincare should be developed with care, knowledge and respect for the people who use it.

That means understanding the ingredients, paying attention to formulation details and taking product safety seriously, even when those details are not visible to the customer.

At Remih, our philosophy is simple: skincare should be about informed choices, thoughtful formulation and helping people care for their skin with confidence.

Because a good skincare product should do more than feel luxurious.

It should be developed responsibly, with its safety and quality carefully considered.

And that is one of the lessons I believe every serious cosmetic formulator should understand: preservation is not just about adding a preservative. It is about proving that your preservation system works.

 Founder, Remih Skincare

Let Your Light Shine.

A note for formulators: Phenoxyethanol is permitted as a cosmetic preservative at up to 1% in the EU. The appropriate concentration and preservation system depend on the specific formula and applicable requirements. A suitable chelator or preservative booster may help, but neither guarantees safety. Finished-product testing and an appropriate cosmetic safety assessment remain essential.

References

• European Commission, Scientific Committee on Consumer Safety (SCCS), Opinion on Phenoxyethanol, SCCS/1575/16.

• ISO 11930:2019, Cosmetics — Microbiology — Evaluation of the antimicrobial protection of a cosmetic product.