The modern way of preserving a product means making a product unattractive for germs but highly attractive for consumers without causing any irritation. In modern cosmetics, mild preservation plays a key role and is more important than ever. Environmental conditions are becoming increasingly challenging for our skin and preservation strategies are in the spotlight because most listed preservatives have negative side effects, while restrictions are increasing and permitted dosages decreasing. The average consumer does not pay much attention to preservation strategy. Nevertheless, consumers want a mild cosmetic product with a high stability and long shelf life. The formulator’s point of view is different because preservation is often more challenging than one would expect.

Bacteria, yeast and mould are an indispensable element of life and evolution. On the one hand, bacteria on our skin and in our digestive system are highly functionally necessary, while on the other hand, we aspire to protect our food and cosmetics against undesirable contamination. Killing bacteria, yeast and mould is less of a challenge than finding the right balance for each individual formulation and maintaining mildness.

So how would the perfect preservative look? It should be natural, acting independently of pH values and working in all formulations. It should also be transparently soluble in water, mild, stable, odourless and colourless and even be inexpensive. The bad news is that such a preservative does not exist.

We always need to find the perfect solution for individual requirements, meaning that obstacles need to be detected early in order to avoid risks and pitfalls. A guiding principle of this nature, however, confronts cosmetics manufacturers with typical questions for each new development or for the replacement of listed preservatives. Cosphatec GmbH has more than 15 years of experience in product protection with a focus on preservation and alternative microbiological solutions. In this article, we will be giving you an overview of frequently asked questions, general challenges and a guide on how to increase the mildness of your formulations.

What is the difference between listed preservatives and non-listed preservatives? What are the advantages and disadvantages?

In order to answer these questions, we need to start by diving into the history of preservation while also concentrating on the rapid development from the last 15 years and the latest trends. The first signs of preservation date back to 5000 B.C., when grapes were dried or used to prepare wine and vinegar. The Romans mastered many preservation techniques that are still used today. Vegetables were covered by oil, fruits preserved by honey and other food was salted or boiled in salted water. In the late Roman Byzantine Empire, medical findings led to the discovery of distillation, and this also saw the beginning of perfume development and the use of alcohol for preservation.

The development of synthetic preservatives in the 19th and 20th century led to the breakthrough of broadband preservation. In 1855, formaldehyde was discovered and ten years later, technical production was made a reality. Over the course of the next 100 years, formaldehyde donors such as DMDM hydantoin and Bronopol were used. The invention of parabens in 1930 had a significant influence on the market and greatly simplified preservation. These esters of p-hydroxybenzoic acid boasted great efficiency and acceptable water solubility, covered a broad pH range of 3.0 – 7.0 and were inexpensive. However, every product has its zenith and the situation changed.

Since 1953, more and more toxicological research centres have been established, which have gradually put a dampener on the use of several synthetic preservatives. Even a couple of dangerous side effects starting from allergic reactions and hormone-influencing effects right up to carcinogenic potential were able to be identified. Knowledge of all this led to several substances coming under suspicion. Today, some substances are banned entirely and the use of most early synthetic preservatives has been restricted. Nevertheless, parabens are still used in mass market products, but more and more formulators are already screening the market for alternatives. For a long time, phenoxyethanol was a very common preservative but nowadays it has also come under fire. This often marks the beginning of a deadly struggle for a raw material and can be seen as negative marketing. The experiences and opinions of consumers have a huge influence on the dynamic of the market and are ultimately decisive. This means that mildness is more than having non-irritating ingredients, but also includes a lack of hidden negative side effects or negative connotations in consumers’ minds.

Unfortunately, many common traditional preservatives have negative side effects. Before examining the traditional preservatives, we first need to define the word ‘preservative’. In general, two definitions exist. From a microbiological point of view, all substances with an antimicrobial effect are defined as preservatives. This includes oil, honey, sugar, organic acids, alcohols, diols, synthetic substances, etc. The European Cosmetics Regulation provides a different definition: all antimicrobial substances which have only one function (to preserve) are listed as preservatives. Substances with additional positive functions are not listed as preservatives. This is interesting because nearly all of these Multifunctionals have a much better toxicological rating, fewer negative side effects, additional useful positive effects and better marketing opportunities, and are not limited in terms of their permitted dosage, whereas the US market works a little bit differently.
When selecting recommended antimicrobials, many companies follow the whitelists of Skin Deep, Sephora, Whole Foods or GRAS. Unlike the EU, the US market often uses “free-from” statements to underline the mildness of their products. A closer look reveals that the EU and US market are more similar than one might assume. All Multifunctionals in our portfolio are not listed as preservatives in the European Cosmetic Regulation and have the best rating in the US databases mentioned such as Skin Deep.

Therefore, Multifunctionals are the first choice when it comes to increasing the mildness of a formulation by providing a higher level of skin compatibility. As a result, unpleasant side effects can be avoided and additional positive effects reaped as benefits. The worldwide production volume of standard preservatives used for mass market products is much higher and therefore prices are lower. While this might change in the future, it currently needs to be considered. In other words, the price of alternative preservation might be higher at first glance, but taking into consideration all the positive effects natural alternatives bring for the product, the consumer and the environment, it should not be viewed as a disadvantage but rather as an opportunity to change for the better.

Where does the trend of replacing traditional preservatives originate?

It seems that in the last ten years, progress has sped up more than ever. Why? Scientific research, safety reports and toxicological as well as irritation tests are just some pieces of the puzzle. Test magazines, cosmetics websites and ratings apps for smartphones are further powerful tools with a strong influence on consumers’ opinions and needs. Whereas in the past, a certain level of chemical knowledge was necessary to understand the INCI of cosmetic products, in modern times, smartphone apps make it very easy to gain a quick and straightforward overview of substances and their individual rating just by scanning the product.

Nevertheless, these platforms can be unfair and misleading if they don’t handle the individual rating of raw materials transparently. Environmental conditions are changing across the globe and pandemics like that of Covid-19 are also influencing consumer opinions. These tools and the growing awareness concerning chemical components is amplifying the pressure on cosmetics producers and increasing the number of newly developed healthy ingredients alike. Even large multi-national corporations have started to replace controversial substances with natural alternatives.

Does the replacement of listed preservatives with alternative antimicrobials influence the shelf life of the product?

While many formulators understand that non-listed preservatives are a good method of increasing the mildness of a formulation, they are concerned that these Multifunctionals may be less efficient and unable to provide the same shelf life for the final product. These doubts are unfounded. As mentioned previously, from a microbiological point of view, Multifunctionals also boast a strong antimicrobial efficiency. Nevertheless, the main challenge always lies in finding the most efficient combination for each unique formulation. In general, using a combination of two or three antimicrobials with synergetic effects is recommended. By using Multifunctionals, you can lower concentration, use more sustainable ingredients, reduce economic and environmental costs and increase the mildness of the product.

What should be considered in personal choices and how can pitfalls be avoided?

Each company has individual requirements and different strategies. In bigger companies, strategies might differ from product line to product line. Therefore, the first thing you need is to know what you are looking for and what strategy you are pursuing to produce skin-friendly products.

  • If you are producing natural products and following e.g. the COSMOS-certification, you are limited to COSMOS-approved Multifunctionals.
  • If you do not need COSMOS-certification, you can also choose synthetic substances. Often, chemically identical synthetic substances are available, which can be excellent at reducing costs.
  • If listed and mild preservatives are an option for you, you can also use blends such as the Cosphagard series, which are combinations of mild preservatives and multi-functionals.
  • A further option would be to lower the concentration of your preservatives by boosting antimicrobial efficiency using Multifunctionals.

The application area of the product, type of formulation and even the local market also need to be considered. Face creams require a milder preservation system than body lotions. The type of formulation is also a key factor. A typical face mask applied to a sensitive face with a skin exposure time of 20-30 minutes will need very mild ingredients. Furthermore, average skin sensitivity also poses a challenge. Typical Western or African skin types are less sensitive compared to the average Asian skin type. Nowadays, exporting products to the Chinese market is very popular due to the high number of consumers. In addition, the requirements for Asian markets are more challenging. White skin is still very popular in Asia and many whitening agents are aggressive to the skin. Consumers cause irritation to their skin because they want to follow local beauty ideals. After this treatment, they apply face masks to alleviate the irritation. This is a very good example of how challenging the situation can be.

Are certified products more skin-friendly and which certification label should I trust more?

Sometimes, the situation can become very confusing and it is not easy to retain an overview. It seems as if for each new trend, a new certification label pops up. All these labels have different requirements and can be hard to keep track of, particularly for manufacturers who export their products and are thereby obligated to fulfil local requirements from other countries. Despite this, today it is highly recommended to reassess in particular the antimicrobial system of cosmetic formulations more than ever. Most certification labels focus on natural ingredients and on average, the final products are more skin-friendly. As a responsible formulator, it is important not to follow every rule blindly. For example, a vegan product may be full of harmful ingredients and natural raw materials can also cause irritation. As Paracelsus said:

“Poison is in everything and no thing is without poison.
The dosage makes it either a poison or a remedy.”

Are new innovative antimicrobials the best choice for preparing mild formulations?

Scientific research is very important. The number of resistant germs is growing and the wider the choice of suitable antimicrobials, the easier it is to find the best solution for an individual formulation. We are continuously screening not only the market and but also nature for new antimicrobials and extracts, but frankly speaking, research often means that by solving one problem, two new problems pop up. Parabens and formaldehyde were once declared as the “perfect new substances” for preservation systems. However, the negative side effects were only detected many years later.

It is impossible to know what kind of side effects might be detected in the future. Nowadays, toxicology centres have a lot of experience and are highly professional, meaning that they will test substances precisely and therefore very likely expose any side effects. The risks are obviously higher with new chemically produced molecules compared to naturally sourced substances but research is much more significant. The identification of synergetic effects plays a key role in modern and skin-friendly cosmetics. The better the understanding of the mode of action and interactions of antimicrobials, the lower the concentration required to ensure no efficiency is lost. In general, we recommend combining two or three different antimicrobials. If one antimicrobial needs to pass the bacteria membrane and the other one attacks the membrane, efficiency can be increased by using two antimicrobials. Another very good example is the solubility of antimicrobials: many of the most effective substances are soluble in oil. Germs grow in the water phase, meaning hydrophobic substances also need to be pushed into the water phase, otherwise they will not be effective in emulsions. You can make the water phase more attractive for those substances by using diols or co-emulsifiers that are present in the interphase and simultaneously act as a solvent for oil-soluble antimicrobials. We expect new molecules and new antimicrobial extracts to be developed as we gain more knowledge about natural processes and billions of years of evolution. Nevertheless, improving existing substances to work in a more effective way is also becoming increasingly important.

Finally, history shows us that the current classification is just a snapshot of the current toxicological knowledge basis and it will be interesting to see what new insights the future will bring. Thus, improving well-known substances represents another part of research. Well-proven antimicrobials which have been used for decades without any concerns are like raw diamonds. Allow me to clarify this with an example: the combination of levulinic acid (Cosphaderm® LA-T) and anisic acid (Cosphaderm® pAS natural) is very often used in baby care products as well as in products for sensitive skin. A deficiency was considered within the workflow – but we already have a solution. First, you need to form the salt of anisic acid to dissolve it in water and at the end of your formulation, you need to reduce the pH value to benefit from the antimicrobial efficiency of the acid. Due to this extensive workflow, we created Cosphaderm® Sodium LAAS. At first glance, this product seems inconspicuous but the details are what make the difference. Transforming both natural acids into salts combined with a spray drying process results in a new product that is far more user-friendly and more sustainable. No further dissolution steps of the acids are needed and the concentration of actives in the mixture can be increased to a maximum. This not only reduces packaging and transportation costs but also storage space.

In conclusion, mild products and an excellent skin feeling do not contradict each other. Nowadays, technical progress allows us to produce very pure and natural high-class raw materials. Potential allergens or solvents that might appear during the extraction or production process can be removed completely. Cosmetic manufacturers need to realise that consumers are paying more attention to ingredients and that the trend of more naturality is increasing rapidly. We should and can learn from nature! The preservative system plays a key role regarding mildness. We need to find a way to stabilise formulations without risking skin-friendliness. While costs for natural solutions are higher, these represent just a small percentage of the total calculations, as the environment also has to be taken into consideration. Often, actives and dyes have a much higher influence on final costs. Even for mass market products, there is always room for improvement – even if this is done step by step:

In the first stage, preservatives under criticism can be replaced with mixtures of well-tolerated and mild preservatives boosted by antimicrobial Multifunctionals. The second stage is represented by synthetic Multifunctionals with the major advantage of additional benefits for marketing and a lack of restrictions. Usually, they have the best rating on raw material databases and ratings portals. Finally, the last stage is to increase the shelf life of the product with the help of natural-certified antimicrobials which completely replace traditional preservatives or synthetic substances.

This broad product portfolio is a relief for every cosmetics manufacturer because many substances are offered as both a natural and a synthetic version. Once an efficient antimicrobial system has been identified, it is easy to start with the synthetic versions and simply replace them with the chemically identical natural versions if certification is required.

For each individual formulation, the best price/efficiency ratio needs to be identified. If you want to formulate for mildness, you should consider seeking in-depth advice from these experts.