The modern way of preserving a product means making it unattractive to germs but highly attractive to the consumer without causing irritation. For modern cosmetics, compatible preservation plays a key role and is more important than ever. Environmental conditions are becoming more challenging for our skin and preservation strategy is taking centre stage as most of the approved preservatives have negative side effects, restrictions are increasing and permitted dosage levels are decreasing. The average consumer does not pay much attention to preservation. At the same time, consumers want a compatible cosmetic product with high stability and a long shelf life. Formulators have a different perspective, as preservation is often more difficult than expected.
Bacteria, yeasts and moulds are an indispensable part of life and evolution. On the one hand, bacteria on our skin and in our digestive system are of great functional importance, but on the other hand, we want to protect our food and cosmetics from unwanted contamination. Killing bacteria, yeasts and moulds is less of a challenge than finding the right balance for each individual formulation and maintaining tolerability.
So what would the absolutely perfect preservative look like?
It should be natural, pH-independent and effective in all formulations. It should also be transparent, water-soluble, compatible, stable, odourless, colourless and, above all, inexpensive. The bad news is that no such preservative exists.
It is always a matter of finding the perfect solution for your individual requirements and identifying obstacles at an early stage in order to avoid risks and pitfalls. However, this guiding principle raises typical questions for cosmetics manufacturers whenever they develop new products or replace listed preservatives. Cosphatec GmbH has more than 120 years of experience in product protection with a focus on preservation and alternative microbiological solutions. In this article, we provide an overview of frequently asked questions, common challenges and a guide to increasing the compatibility of your formulations.
What is the difference between listed and unlisted preservatives? What are the advantages and disadvantages?
To answer these questions, we need to look at the history of preservation from the very beginning and also focus on the rapid developments of the last 15 years and the latest trends. The first evidence of preservation dates back to 5000 BC, when grapes were dried or used to make wine and vinegar. The Romans mastered many preservation techniques that are still used today. Vegetables were stored in oil, fruit was preserved with honey, and other foods were salted or cooked in salt water. In the late Roman-Byzantine Empire, medical knowledge led to the discovery of distillation, the beginning of the development of perfume, and the use of alcohol for preservation.
The development of synthetic preservatives In the 19th and 20th centuries, broadband preservation became a thing. Formaldehyde was discovered in 1855, and ten years later, people figured out how to make it. Over the next 100 years, formaldehyde donors like DMDM hydantoin and bronopol were used. The invention of parabens in 1930 had a major impact on the market and greatly simplified preservation. These esters of p-hydroxybenzoic acid were highly effective, had acceptable water solubility, covered a wide pH range from 3.0 to 7.0, and were inexpensive. However, every product has its zenith, and the situation has changed.
Since the 1950s, more and more toxicological research centres have been established, which have gradually put an end to many synthetic preservatives. A number of dangerous side effects have even been identified, ranging from allergic reactions and hormone-disrupting effects to carcinogenic potential. All of this has led to several substances coming under suspicion. Today, some substances are completely banned, and the use of most early synthetic preservatives has been restricted. Nevertheless, parabens are still used in mass-produced products, although more and more formulators are already looking for alternatives. Phenoxyethanol was a very common preservative for a long time, but is now also in the firing line. This often rings the death knell for a raw material, as it generates negative marketing. Consumer experiences and opinions have a major influence on market dynamics and are ultimately decisive. This means that compatibility means more than just a non-irritating ingredientbut 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 we get to traditional preservatives, we must first define the word preservative. In general, there are two applicable definitions. From a microbiological point of view, all substances with antimicrobial effects are preservatives. These include oil, honey, sugar, organic acids, alcohols, diols, synthetic substances, etc. According to the European Cosmetics Regulation the definition is different: all antimicrobial substances that have only one function (preservation) are listed as preservatives. Substances with additional positive functions are not listed as preservatives. This is interesting because almost all of these so-called Multifunctionals have a significantly better toxicological classification, fewer negative side effects, additional beneficial effects, better marketing opportunities and no restrictions on the permissible dosage.
The US market, on the other hand, functions somewhat differently:
When selecting recommended antimicrobial agents, many companies refer to the whitelists published by Skin Deep, Sephora, Wholefood or GRAS. Unlike in the EU, the US market often uses the term „free from“ statements to emphasise the compatibility of the products. On closer inspection, however, it becomes apparent that the EU and US markets are more similar than one might generally assume. All Multifunctionals from our portfolio are not listed as preservatives in the European Cosmetics Regulation and have the best rating in the mentioned US databases such as Skin Deep.
Therefore, Multifunctionals which First choice for increasing the tolerability of a formulation and offer greater skin compatibility. This allows you to avoid unpleasant side effects and benefit from the additional positive effects. The global production volume of standard preservatives used in mass-produced products is much higher, and prices are therefore lower. This may change in the future, but must be taken into account today. This means that the price of an alternative preservative may be higher at first glance, but considering all the positive effects that natural alternatives have on the product, the consumer and the environment, this should not be seen as a disadvantage, but rather as an opportunity for change for the better.
Where does the trend to replace traditional preservatives come from?
It seems that progress has accelerated more than ever in the last ten years. Why? Scientific research, safety reports, and toxicological and irritation tests are just a few pieces of the puzzle. Test magazines, cosmetics websites, and smartphone review apps are other powerful tools that have a strong influence on consumer opinions and needs. Whereas in the past a certain amount of chemical knowledge was necessary to understand the INCI of cosmetic products, today's smartphone apps make it very easy to quickly and easily scan a product to get an overview of its ingredients and their individual ratings.
Nevertheless, such platforms can be unfair and misleading if they do not make the individual assessment of raw materials transparent. Environmental conditions are changing worldwide, and pandemics such as the current Covid-19 are also influencing consumer opinion. As a result of these instruments and growing awareness of chemical ingredients, pressure on cosmetics manufacturers is increasing, as is the number of newly developed healthy ingredients. Even large multinational companies have begun to replace controversial substances with natural alternatives.
Does the replacement of listed preservatives with alternative antimicrobials influence the shelf life of the product?
Many formulators know that unlisted preservatives are a good option for increasing the tolerability of a formulation. However, they fear that these Multifunctionals may be less efficient and unable to provide the same shelf life for the final product. These doubts are unfounded. As already mentioned, Multifunctionals also have a strong antimicrobial effect from a microbiological point of view. However, the challenge is always to find the most effective combination for each individual formulation. In general, it is recommended to use a combination of two or three antimicrobial agents that have a synergistic effect. 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 when making a personal decision and how can pitfalls be avoided?
Each company has individual requirements and different strategies. In larger companies, strategies may vary from product line to product line. So, first and foremost, you need to know what you are looking for and what strategy you are pursuing in the manufacture of skin-friendly products.
- If you manufacture natural products and comply with COSMOS certification, for example, you are COSMOS-certified. Multifunctionals restricted.
- If you do not require COSMOS certification, synthetic fabrics are also available. Chemically identical synthetic fabrics are often available, which are ideal for reducing costs.
- If listed and compatible preservatives are acceptable to you, you can also use mixtures such as Cosphagard series use combinations of compatible preservatives and multifunctional agents.
- Another option would be to reduce the concentration of your preservatives by boosting antimicrobial efficiency using Multifunctionals .
The product's area of application, the type of formulation and even the local market should also be taken into account. Face creams require a more compatible preservation system than body lotions. The type of formulation is also of great interest. A typical face mask, which is applied to the sensitive face and remains on the skin for 20–30 minutes, requires very compatible ingredients. In addition, average skin sensitivity also poses a challenge.
Other common pitfalls include the correct pH value and negative interactions between certain ingredients. The pH value chosen for face creams and eye serums that come into contact with the mucous membranes of the eyes can cause irritation. The pH value of our skin is 5.5. This means that a final pH value of 5.5 is strongly recommended for typical skin care products. On the one hand, a pH value of 5.5 is compatible with our skin, and on the other hand, there is a wide range of suitable preservatives or multifunctional agents to choose from, as almost all of them are effective at this pH value. However, the pH value of our tear fluid is 7.35, and although an eye serum with a pH value of 5.5 is good for the skin around the eyes, it can be slightly irritating to our eyes. The interaction of ingredients can be a great advantage, but also a challenge. Penetration enhancers are wonderfully suited to increasing the effectiveness of active ingredients. By combining active ingredients and penetration enhancers, the active ingredients can penetrate deeper into the skin. Commonly used diols belong to the group of penetration enhancers. They increase the stability of emulsions by reducing particle size and support antimicrobial efficacy by attacking the cell wall or membranes of germs. The disadvantage, however, is that they can also increase the irritation potential of slightly irritating ingredients.
Are certified products more skin-friendly, and which quality seal should I trust more?
Sometimes it can be very confusing, and it is not easy to keep track of everything. It seems as if a new quality mark appears for every new trend. All these labels have different requirements, and it can be difficult to keep track of them all. This is especially true for manufacturers who export their products and are therefore obliged to meet the local requirements of other countries. This makes it more important than ever to check the antimicrobial system of cosmetic formulations in particular. Most quality seals focus on natural ingredients, and the end products are, on average, more skin-friendly. As a responsible formulator, you should not blindly follow every rule. For example, a vegan product can be full of harmful ingredients, and even natural raw materials can cause irritation. How Paracelsus said:
„All things are poison, and nothing is without poison;
It is the dose alone that determines whether something is poisonous or not.“
Are new innovative antimicrobial agents the best choice for producing compatible formulations?
Scientific research is very important. The number of resistant germs is increasing, and the greater the selection of suitable antimicrobial agents, the easier it becomes to find the best solution for an individual formulation. We are constantly searching not only the market but also nature for new antimicrobial agents and extracts – but frankly speaking, research often means that solving one problem creates two new ones. Parabens and formaldehyde were once hailed as the „perfect new substances“ for preservation systems. However, their negative side effects were only discovered many years later.
It is impossible to know what kind of side effects might be detected in the future. Nowadays, toxicology research centres have a wealth of experience and work in a highly professional manner. This means that substances are tested thoroughly and side effects are highly likely to be detected. Of course, the risks are higher with new, chemically produced molecules than with naturally derived substances. However, research is achieving much more. The identification of synergistic effects plays a key role in modern, skin-friendly cosmetics. The better we understand the mode of action and interactions of antimicrobial agents, the lower the concentration required without compromising efficacy. It is generally recommended to combine two or three different antimicrobial agents. If one antimicrobial agent has to pass through the bacterial membrane and another attacks the membrane, the effectiveness can be increased by using two antimicrobial agents. Another very good example is the solubility of antimicrobial agents: many of the most effective substances are soluble in oil. Since germs grow in the aqueous phase, hydrophobic substances must also be introduced into the aqueous phase, otherwise they are not effective in emulsions. The aqueous phase can be made more attractive to these substances by using diols or co-emulsifiers, which are present in the intermediate phase and also serve as solvents for oil-soluble antimicrobial agents. With increasing knowledge of natural processes and billions of years of evolution, new molecules and new antimicrobial extracts are likely to be developed. However, improving the effectiveness of existing substances is also becoming increasingly important.
Finally, history teaches us that the current classification is only a snapshot of the current toxicological knowledge base, and it will be interesting to see what new insights the future will bring. Improving known substances is therefore another part of the research. Proven antimicrobial agents that have been used without concern for decades are like rough diamonds. Here is an example: the combination of levulinic acid (Cosphaderm® LA-T) and anic acid (Cosphaderm® pAS natural) is very commonly used in baby care products and products for sensitive skin. A deficiency was identified in the workflow – but we already have a solution. First, the salt of the anise acid must be formed in order to dissolve it in water, and at the end of the formulation, the pH value must be lowered to utilise the antimicrobial effectiveness of the acid. Due to this complex workflow, we have developed Cosphaderm® Sodium LAAS : At first glance, this product may seem unremarkable, but it is the details that make the difference. The conversion of the two natural acids into salts in combination with a spray drying process results in a new product that is much more user-friendly and also more sustainable. No further dissolution steps of the acids are necessary, and the concentration of the active ingredients in the mixture can be increased to a maximum. This not only saves packaging and transport costs, but also storage space. In summary, it can be said that Compatible products and excellent skin feel are not a contradiction.. Today, technological advances enable us to produce very pure, natural raw materials of high quality. Potential allergens or solvents that could arise during the extraction or production process can be completely eliminated. Cosmetics manufacturers must recognise that consumers are paying increasing attention to ingredients and that there is a growing trend towards more natural products. We should and can learn from nature! The preservation system plays a key role in compatibility. We need to find a way to stabilise formulations without compromising skin friendliness. Natural solutions are more expensive, but they only account for a small percentage of the total cost, as the environment must also be taken into consideration. Active ingredients and colourants often have a much greater impact on the final cost. Even with 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 be reinforced. The second stage consists of synthetic Multifunctionals which have the great advantage of offering additional marketing benefits and no restrictions. They usually have the best ratings in raw material databases and review portals. The final step is to extend the shelf life of your product using naturally certified antimicrobial substances that completely replace conventional 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.
