Phenoxyethanol and Ethylhexylglycerin, commonly supplied as PE91 or similar preservative blends, is widely used in cosmetic and personal care formulations. However, choosing a suitable preservative is only the first step.

During formulation development, manufacturers may encounter questions about solubility, pH compatibility, surfactants, emulsifiers, processing temperature, dosage, and preservation performance.

This guide focuses on practical formulation considerations when working with PE91 rather than simply explaining what PE91 is.

If you are looking for the product specification or bulk supply, see our Phenoxyethanol & Ethylhexylglycerin PE91 product page.

1. Why Can PE91 Cause Formulation Problems?

PE91 contains Phenoxyethanol and Ethylhexylglycerin. The physical behavior of the preservative in a finished product depends not only on the preservative itself but also on the complete formulation.

Important factors include:

• pH

• Water content

• Surfactants

• Emulsifiers

• Oils and emollients

• Solubilizers

• Processing temperature

• Packaging

• Microbial risk

• Final preservative concentration

Therefore, a preservative system that works well in one formulation may require adjustment in another.

2. Is PE91 Water Soluble?

PE91 should not be treated as a freely water-soluble ingredient.

The incorporation method depends on the commercial grade and the complete formulation. Phenoxyethanol has limited water solubility, while Ethylhexylglycerin has different solubility characteristics.

For aqueous formulations, formulators should pay attention to:

• Addition method

• Mixing efficiency

• Surfactant system

• Solubilizers

• Final concentration

• Temperature during processing

If the finished product becomes cloudy or shows separation after adding PE91, the problem may be related to the formulation system rather than the preservative alone.

What should you do if PE91 causes cloudiness?

First check:

1. The actual dosage of PE91

2. The order of addition

3. Mixing speed and time

4. Surfactant concentration

5. Solubilizer level

6. Oil phase composition

7. Final pH

8. Temperature during processing

A small laboratory compatibility test is recommended before scaling up production.

3. What pH Range Can Be Considered?

PE91-based preservation systems are used across a range of cosmetic formulations, but the optimal performance depends on the complete formulation.

Do not select a preservative based only on a nominal pH range.

The final formulation should be evaluated for:

• pH

• Water activity

• Ingredient interactions

• Microbial challenge

• Storage stability

For commercial products, preservation efficacy should be confirmed by appropriate testing.

4. PE91 and Surfactants

PE91 can be used in many surfactant-based formulations, including:

• Shampoos

• Body washes

• Facial cleansers

• Liquid soaps

• Hand washes

• Cleansing products

However, surfactants can influence preservative availability and antimicrobial performance.

When developing a surfactant-based product, evaluate PE91 together with the complete surfactant system rather than testing the preservative separately.

A useful laboratory approach is to compare:

Base formula → PE91 added → accelerated stability → microbial challenge test

This can help identify whether a formulation change affects preservation performance.

5. PE91 in Emulsions, Creams and Lotions

PE91 can be considered for leave-on emulsions such as:

• Face creams

• Body lotions

• Moisturizers

• Serums

• Cream masks

In emulsions, preservative distribution between the water phase, oil phase and interfaces can affect efficacy.

The following factors should therefore be evaluated:

• Emulsion type

• Oil phase

• Emulsifier system

• pH

• Water activity

• Packaging

• Processing conditions

A formulation that looks physically stable may still require preservation efficacy testing.

6. When Should PE91 Be Added?

The appropriate addition stage depends on the formulation and manufacturing process.

For heat-sensitive formulations, PE91 is often evaluated during the cooling stage rather than being exposed unnecessarily to prolonged high temperatures.

However, there is no universal addition temperature for every formula.

Always follow the technical specification of the commercial grade being used and confirm the effect of processing conditions through stability testing.

7. How Much PE91 Should Be Used?

There is no single dosage that works for every cosmetic formulation.

The appropriate concentration depends on:

• Product category

• Microbial risk

• Water activity

• pH

• Raw materials

• Packaging

• Manufacturing conditions

• Target market regulations

Do not select the dosage simply because another product uses the same concentration.

For example, a facial cream, shampoo, wet wipe solution and liquid cleanser may require different preservation strategies.

The final use level should be determined through formulation development and preservation efficacy testing.

8. PE91 and Wet Wipes

Wet wipes are a particularly important application because they contain a high proportion of water and may be exposed to repeated microbial contamination during use.

When developing a wet wipe formulation, consider:

• Water quality

• pH

• Surfactants

• Humectants

• Plant extracts

• Packaging

• Preservative distribution

• Finished-product challenge testing

PE91 can be considered as part of a wet wipe preservation system, but its suitability should always be validated in the actual formulation.

9. Why Does PE91 Sometimes Fail a Challenge Test?

A failed preservation test does not necessarily mean that PE91 is an unsuitable preservative.

Possible causes include:

Incorrect dosage

The concentration may be insufficient for the microbial risk of the formulation.

Ingredient interaction

Surfactants, emulsifiers, proteins, botanical extracts and other raw materials can influence preservative performance.

Poor preservative distribution

The preservative may not be adequately available in the phase where microorganisms are growing.

High microbial load

Raw materials, process water or manufacturing equipment may introduce excessive microbial contamination.

Packaging-related contamination

Repeated opening or dispensing can increase the microbial challenge during product use.

Formulation pH

The formulation environment can influence antimicrobial performance.

For this reason, troubleshooting should consider the entire formulation rather than simply increasing the preservative concentration.

10. PE91 vs. Phenoxyethanol Alone

PE91 combines Phenoxyethanol with Ethylhexylglycerin, while Phenoxyethanol alone contains only one preservative ingredient.

The choice depends on the formulation strategy.

Neither option should automatically be considered suitable for every formulation.

For a detailed comparison, see our guide to Phenoxyethanol vs. PE91.

11. PE91 vs. Phenoxyethanol + Chlorphenesin

PE91 is not the only Phenoxyethanol-based preservative system.

Another option is a Phenoxyethanol + Chlorphenesin blend.

The two systems have different compositions and should not be treated as interchangeable without formulation testing.

If you are comparing these two systems, consider:

• Product type

• pH

• Regulatory requirements

• Ingredient compatibility

• Preservation test results

• Target market

See our Phenoxyethanol + Chlorphenesin preservative page for product information.

12. How to Troubleshoot a PE91 Formulation

When a formulation has a problem, use a step-by-step approach.

Step 1: Check the raw material

Confirm the PE91 specification, batch number, appearance and storage history.

Step 2: Check the formulation

Review:

• pH

• Water content

• Surfactants

• Emulsifiers

• Oils

• Botanical extracts

• Fragrance

• Other antimicrobial ingredients

Step 3: Check the manufacturing process

Review the:

• Addition sequence

• Mixing conditions

• Processing temperature

• Cooling procedure

• Filling process

Step 4: Check the packaging

Evaluate whether the packaging protects the product from repeated microbial contamination.

Step 5: Perform preservation testing

Physical stability and microbial preservation are different tests.

A formula can remain visually stable while still failing a microbial challenge test.

13. What Should Cosmetic Manufacturers Ask Their PE91 Supplier?

Before purchasing PE91 for commercial production, request:

• TDS

• SDS

• COA

• INCI information

• Product specification

• Batch information

• Shelf life

• Storage conditions

• Packaging information

• MOQ

• Sample availability

For international procurement, also confirm the documentation required for the destination market.

14. PE91 Supplier for Cosmetic and Personal Care Applications

Easychem supplies Phenoxyethanol and Ethylhexylglycerin preservative blends for international B2B customers.

Our PE91-related products are intended for applications including cosmetics, personal care, wet wipes and selected home care formulations.

For product qualification, buyers can request technical documents and samples before commercial purchasing.

Request PE91 Technical Information

Please provide:

• Your application

• Required quantity

• Destination country

• Packaging requirement

• Required documents

We can then provide the relevant product specification, technical documents and quotation.

Frequently Asked Questions

Why does PE91 make my formulation cloudy?

Cloudiness can be related to solubility, addition sequence, surfactants, oils, solubilizers or other formulation components. Test the preservative in the complete formulation rather than evaluating PE91 alone.

Can PE91 be used in shampoos?

PE91 can be considered for shampoo and other rinse-off formulations. The finished product should be evaluated for compatibility and preservation efficacy.

Can PE91 be used in wet wipes?

Yes, PE91 can be considered for aqueous wet wipe formulations. However, water quality, pH, raw materials, packaging and microbial challenge testing are important.

Can I replace Phenoxyethanol with PE91 directly?

Not necessarily. PE91 contains Ethylhexylglycerin in addition to Phenoxyethanol, so the formulation should be recalculated and tested rather than making a direct one-to-one substitution.

Does a higher PE91 dosage always provide better preservation?

Not necessarily. Preservation performance depends on the complete formulation and microbial challenge. Increasing the dosage should not replace proper formulation development and testing.

What information should I provide when asking for a PE91 sample?

Tell the supplier your application, target quantity, destination country and any specific technical requirements. This helps the supplier provide the appropriate grade and documentation.

Conclusion

PE91 can be a convenient preservative system for many cosmetic and personal care formulations, but successful preservation depends on more than selecting the right ingredient.

pH, solubility, surfactants, emulsifiers, processing conditions, packaging and microbial challenge testing should all be considered during formulation development.

If you are experiencing a specific PE91 formulation problem, share your formula type, pH, PE91 dosage and the problem you are seeing, and a supplier or formulation specialist can help identify possible causes.