Overview of preservatives in cosmetics

Many people think preservative is not a good thing, it’s often criticized, it does have a link to allergies (apart from perfume, preservatives are the second most important allergen), but preservatives are not the enemy, they can help keep cosmetics safe and last longer. We think the name preservative would be much better accepted if it was replaced with “freshness”.

What is preservative

According to the Cosmetic Regulation EC 1223/2009: “any substances which are exclusively or mainly intended to inhibit the development of microorganisms in the cosmetic product”.

It works by acting on the cell membranes, cell walls, and enzymes of microorganisms at a number of targets, disrupting cell division and inhibiting bacterial growth and reproduction for the purpose of preserving the quality of cosmetics for the duration of their validity.

However, preservatives are not without their disadvantages. There are many different types of preservatives and excessive and frequent exposure can lead to allergic reactions in the body.

Therefore it is not wise to rely on them or to be caustic about them.

Why cosmetics need preservatives

Cosmetics are prone to bacterial growth for the following reasons, and preservatives ensure that they do not deteriorate during their shelf life.

• The optimal pH of human skin is between 4-6.5 and this range is also the optimal environment for bacterial production (pH 5-8). In general, microorganisms cannot reproduce or survive in cosmetic formulations with a pH of less than 4 or more than 10 and we need preservatives to create an environment where microorganisms should not survive.
• The presence of water and oil provides a good environment for the production of bacteria, both of which happen to be the main ingredients in many cosmetics; in addition, the nutrients in cosmetics provide a good environment for bacteria to promote their growth.
• Cosmetics can easily cause secondary contamination during use (e.g. from hands, from humid and warm environment).
• Organic substances in skin care products break down harmful substances, and preservatives can effectively inhibit this behaviour.

Although the use of preservatives cannot be avoided, we can choose systems that are gentler and less potentially harmful, and toxic to humans.

How many preservatives are available in cosmetics

IIn the USA, the Cosmetic Ingredient Review (CIR) lists all available cosmetic ingredients (including preservatives) and limits in the CIR regulations, but because the regulations do not classify ingredients by function, there is no specific list of permitted preservatives in the U.S. The FDA does not have specific regulations for cosmetic preservatives and, with the exception of color additives, cosmetic products do not require FDA approval is not required before a cosmetic product can be marketed, except for color additives, but the necessary labeling is required to ensure that the public is aware of the product’s ingredients.

In Europe, the Cosmetic Regulation EC 1223/2009 Annex V lists 59 preservatives and their concentration limits that are allowed to be used in cosmetic formulations. Every cosmetic product marketed in the EU must comply with the regulations and annexes. The higher the concentration that can be added, the safer it is.

In Japan, all preservatives approved for inclusion in cosmetics are listed in Annex III (No. 331 of 2000) of the Ministry of Health and Welfare’s “Standards for Cosmetics”.

In China, there are 51 types of preservatives permitted in the Safety Technical Specification for Cosmetics (2015) issued by the National Medical Products Administration.

Which preservatives should we avoid

Based on market research and experimental data, and in conjunction with regulations, the following 3 types of preservatives need to be considered carefully.

1. Methylisothiazolinone/Methylchloroisothiazolinone：which we call MIT, has broad-spectrum bactericidal properties and was allowed to be added to cosmetic products in 2004 by EU cosmetic regulations. However, in recent years, with market research and authoritative scientific experiments, it has been shown to be associated with allergic dermatitis, so the EU has revised its limit: the maximum concentration allowed is 0.0015%.
2. Parabens: yes, the famous Parabens, they are broad-spectrum antimicrobial agents with a wide range of antimicrobial effects on moulds, yeasts and bacteria, but studies have reported that excessive use may cause contact dermatitis and even increase the risk of breast and uterine cancer in women, so the EU limit will be 0.14%.
3. DMDM Hydantoin: belong to the formaldehyde and formaldehyde emitters family, that’s right, the formaldehyde we avoid, has received a lot of attention recently. It works by slowly releasing formaldehyde to kill microorganisms, and although the EU limit for it is 0.6% (which is relatively high), it is better to be safe than sorry.

But don’t assume that preservatives other than these three categories are safe, we should trust authoritative experimental data and regulations.

Which preservatives are safer

This is a difficult question to answer; the safety of preservatives takes a long time to test. Some new preservatives may appear to be safe when they first come out due to the lack of clinical and usage information, but as they are used on a large scale, more and more adverse reactions may be detected. To compare the safety of preservatives side-by-side is a cumbersome task and we can only analyze them based on the available data.

1. Phenoxyethanol: one of the most widely used preservatives and a relatively safe preservative. Phenoxyethanol is generally effective against fungi and is rarely used alone, but is usually used in a 9:1 combination with ethylhexylglycerin and is limited to 1% in cosmetics according to EU regulations.
2. Sodium benzoate: It is used as an acid preservative and they can be found in both stay-on and rinse-off products. The antibacterial activity of this type of preservative is related to its pH and it can only perform well under acidic conditions (the best pH range is 2-6). It has a strong inhibitory capacity against fungi and an average antibacterial capacity. It is limited to 2.5% in cosmetics according to EU regulations.

How to choose a preservative

Overall, an ideal preservative should be stable, compatible, effective at low levels, non-toxic, comply with cosmetic regulations and not be expensive.

• Look at the finished product: for example, some preservatives are suitable for rinse-off and some for stay-on. Pay particular attention to the pH value of the product, which can affect the preservative effect of the product. Generally, organic acid preservatives are more effective in the acid-neutral range, while the effect is greatly reduced in the alkaline range.
• Look at regulations: your preservative must be on the list of permitted preservatives and not exceed the limit. Generally speaking, the higher the limit the safer the ingredient.
• Look at the experiments: yes, we have to do preservative challenge tests to prove whether our theoretical preservative is effective on the whole finished product.

Are there any cosmetics without added preservatives

Yes. But you need to understand the logic behind zero addition. There are several situations where preservatives can be dispensed with.

• Pure water recipes, where preservatives are not needed because there is only water and no “food” for microorganisms.
• Pure oil recipes: there is only oil and no water, so microorganisms cannot grow either.
• Formulationwith a high alcohol content: alcohol can act as an inhibitor of microorganisms, for example in the case of leave-on hand soaps. It should be noted that, according to experimental results, it is preferable to add a preservative to leave-on hand soaps with less than 70% alcohol content.
• Strictly sealed single-use products: products that are strictly disinfected and sealed during the manufacturing process and then discarded after one use. These products have a very short expiry date on opening, such as milk.
• Preservative alternatives: Some ingredients are not included in the preservative system, typically polyols, which provide moisturisation in addition to preservatives, but are weak and often need to be used in combination with other preservatives.

Why are there synthetic preservatives

No single preservative is a panacea, for example, phenoxyethanol is very effective against Pseudomonas aeruginosa, but it may be weak against other bacteria.

So, with the development of this formulation technology, more brands, and clever formulators are opting for the kind of compounding structure preservative system, although you may look like it is adding more types, the total proportion of it is much lower than adding one, and it will also reduce the irritation to our skin.

Another important reason is to increase the PH stability of the product and its compatibility with other ingredients.

What does the future hold for preservatives?

There is interest in finding effective and safe alternative preservatives and compounds with good antimicrobial properties and low toxicity, such as plant extracts, are interesting future alternatives. In addition, the development of preservative-free products is of particular interest today.

In conclusion, cosmetic microbiologists are faced with a great challenge to find new alternative molecules by means of suitable standards, new systems, or improved strategies already implemented.