How to Know When to Use a Preservative

“If a product is anhydrous, surely a preservative isn't necessary?”

“An emulsion requires a preservative – no matter what, right?”

Preservatives are (understandably) a challenge for many artisan formulators. Knowing how (and when) to include them is among the most common type of questions I get from my readers, clients, and students.

I wish there was an easy one-size-fits-all answer.

There are so many different types of cosmetics (and methods of making) that it can be confusing to sort through all the ‘if’s, but’s, and maybes’ of cosmetic preservation.

This article is my attempt at an answer to the many of you who have asked. Please note this is a general guide and will not be able to answer every question you may have.

Rules and Exceptions

Also, as it is with many rules, there are going to be exceptions. For example: despite what you may have been taught/have heard about cosmetics with water content, it is indeed possible to make a safe, long-lasting emulsion without adding a preservative. It is also possible to make an anhydrous product that can result in mouldy growth. Sometimes, including a preservative is going to be a judgement call you will have to make depending on the ingredients you are using, your production method, how your product is packaged, stored, and even how it is used by your customer.

In the guide below, I’ve created categories for the types of formulations and included a few tips as well. I hope you find it useful !

Anhydrous Products

Anhydrous: Minimal Exposure to Moisture

This includes water-free products that have a minimal chance of the contents being exposed to moisture during storage and use.

Examples of ‘minimal moisture’ products are:

• Face oil

• Body oil

• Massage oil

• Balm

• Leave-on oleogels

• Lotion bars

• Ointments

• Hair wax

• Body butters (water-free)

PRESERVATIVE: Unnecessary

TIPS 

• Addition of an antioxidant can help retard rancidity

• Body butter is a term that is used to describe both completely water-free products as well as rich emulsions.

Anhydrous: Some Exposure to Moisture

These are products that have some chance of introduction of moisture during use such as:

• Cleansing balms

• Body scrubs

• Oil-to-milk cleansers

• Pressed powder makeup

PRESERVATIVE: Judgement Call

TIPS

1. Packaging can be a deciding factor (for example if the product is dispensed instead of dipped into).

2. Adding specific instructions can also be a deciding factor (‘keep contents free of moisture- use within 3 months’, etc)

3. Although pressed powder makeup is anhydrous, note that some people will wet their makeup brush before dipping into the product, thereby introducing moisture. If you are selling your products and risk customers (mis)using them in this manner, consider adding preservative or including a disclaimer on the label.

Anhydrous: Moisture Exposure Unavoidable

This includes products where introduction of moisture to the content during use product is a given and includes examples such as:

• Tooth powders

• Wet and apply color cosmetics

• Cleansing powders/grains

• Cleansing balms (packaged in jars where the product is dipped into)

• Exfoliating scrubs (packaged in jars where the product is dipped into)

PRESERVATIVE: Recommended / Judgement Call

TIPS

1. Products such as cleansing powders/grains can be preservative free if explicit instructions are included on the label that the contents must be kept free of moisture. Consider packaging that allows the product to be dispensed without introduction to moisture for optimal shelf life without added preservatives.

2. Some scrubs can be preservative free if sold with spoon/scoop to dispense the product along with clear instruction on the label to keep the contents moisture free.

Anhydrous After Production With High pH

These are products that use water/liquids during production but are cured/dried before use and also have a high pH (generally pH 9-10).

Examples include products such as

• Cold process soap

• Hot process soap

• Beldi soap

PRESERVATIVE: Unnecessary

Anhydrous After Production

These are products that use water/liquids during production but are cured/dried before they are used and include:

• Bath bombs

• Shower steamers

• Solid shampoo bars

• Solid (SYNDET) body wash bars

• Solid conditioner bars

PRESERVATIVE: Unnecessary (in most cases), Judgement Call

TIPS

1. Microbial testing may be the deciding factor.

2. Packaging could be an integral part of the formula. Storage and use could be with explicit instructions. Example: individually wrapped portions/bath bombs that are used immediately after unwrapping.

Products with Water Content

Very Low Water Content

These are products that are predominantly anhydrous but contain a small percentage of ingredients that contain water (such as extracts, tinctures, etc.)

Examples of this type of product includes:

• Cleansing balms (some types)

• Balms (some types)

• Stick deodorants

• Hair styling products (some types)

• Body butters (some)

PRESERVATIVE: Judgement Call

TIPS

1. Microbial testing may be the deciding factor.

2. Packaging could be an integral part of the formula to avoid additional introduction of moisture.

Some Water Content

These products have some content of water but it is not the dominant ingredient. Examples of products of this type can:

• Salves

• Oil-rich lotions

• Rich, thick creams

• Emulsified body butters

PRESERVATIVE: (Generally) Necessary

TIPS

1. Packaging can be a deciding factor as to how much and which type of preservative is required

High Water Content

Water is the predominant ingredient in these products and generally listed first in ingredients list. Examples include:

• Water-based serums

• Lotions

• Creams

• Skin tonics

• Cream Cleansers

• Liquid shampoos

• Liquid hair conditioners

• Ready to use face masks

• Water-based gels (hydrogels)

PRESERVATIVE: (Almost Always) Necessary

TIPS 

1. Packaging can be a deciding factor as to how much preservative is required. Examples: products that are dispensed (pump bottle, serum bottle) or packaged in airless containers may not require as much preservative as a product that is packaged in a wide-neck jar that is dipped into.

Find More (from LisaLise) About Preserving Cosmetics

Overpreserving - as Bad as Underpreserving.

Download a free Natural Preservatives e-book right here

Hurdle Technology - the new Norm for Cosmetics Preservation

Preservative Free Cleansers with Hurdle Technology

Do Tell

Do you work with preservatives in your products? Which kinds of products do you normally add preservative to?

PS: The products in the books below are all preservative free

Make Your Own Preservative Free Natural Cosmetics With 21 Ingredients

Haz tus propios productos cosméticos naturales sin conservantes con 21 ingredientes