Are Preservatives in Cosmetics Safe?
Cosmetics and personal care products are made from a variety of ingredients that naturally break down and can be targeted by a variety of microorganisms including moulds (fungus) and bacteria. Consumers today are used to cosmetics with multi-month shelf lives, and this is down to smart formulations and preservatives. DIY cosmetics and creams without preservatives typically last only a few days or weeks and need to be refrigerated but the use of effective combinations of preservatives can extended the shelf life to 24 months and beyond. Preservatives are synthetic or natural ingredients that are included in formulations to maintain microbiological safety. They do this by limiting the growth of micro-organisms in the product. Below are the most common preservatives used in the cosmetic and personal care industry along with general pros and cons as well as supporting literature. Preservatives get a lot of bad rep in the cosmetic industry, some warranted, some probably not, so let’s look at each of the classes and their safety profiles.
Parabens
Parabens are esters of para-hydroxybenzoic acid, hence then name. They are amongst the most common preservative class used in cosmetic and pharmaceutical products because they are effective, readily available and work against a broad range of microorganisms. All parabens used in these industries are synthetically made although some parabens are identical in chemical structure to chemicals found in nature so can be described as ‘nature-identical’. Despite being used so widely as preservatives, their exact mechanism of action remains unclear. The leading theory is they disrupt a variety of membrane transport processes within bacteria.
Example: Methylparaben
PROS
Inexpensive
Most widely used in the world
Good protection against mould and some bacteria
Designated for use as safe in cosmetics
CONS
Requires an additional preservative for complete bacteria protection
Some data suggests they might possess estrogen activity which may have links to increased rates of breast cancer
Estrogen and steroid hormone disruption concerns
Are Parabens Safe?
Parabens are one of the most divisive class of ingredients within cosmetics now and cherry picking the data can allow anyone to describe parabens as they please ranging from effective and safe to dangerous endocrine disruptors. Most studies looking into parabens are based on a small number or single dose exposure in one type of product. Based on these studies, parabens are considered safe. However, as parabens are used in a wide range of Cosmetics, Pharmaceuticals and Foods, the average person is likely to be exposed to parabens over a prolonged period. In general, parabens are non-irritating and non-sensitising but like with most ingredients, even those considered very safe, a small percentage of people may have inherent sensitivity to parabens.
One of the main points against parabens that really started the bad PR for these group of chemicals was the claim made by the American Cancer Society in 2004 that parabens can be found in the breast tissue of mastectomy patients, but they also specifically said that they did not find evidence that parabens cause cancer. A subsequent review a year later in 2005 concluded that,
It is biologically implausible that parabens could increase the risk of any oestrogen-mediated endpoint, included effects on the male reproductive tract or breast cancer.
This statement is contradicted by some emerging data. More recent issues have focussed on the estrogenic activity of parabens. Parabens have been shown to have weak oestrogenic activity and may interact with estrogen receptors and receptors involved with other steroid hormones . To put this in perspective this ‘weak’ activity was only recorded when parabens were dosed at 25,000 times then level that they are typically found in cosmetic products.
The data on both the cancer causing and the danger of oestrogen-activity of parabens in humans is still being collected. It has been shown in several in vitro and in vivo reviews (here and here) that parabens do interfere with estrogen receptors, and this could be causing unforeseen issues. Much of the furore around parabens seems to stem from early studies which have been challenged and supported in back and forths in the literature but the result is that the industry is now terrified of endocrine disruptors and any ingredient that even has a hint of falling under this category is immediately blacklisted.
Due to the data that is available, I rarely formulate with parabens and only do so when clients specifically ask for their inclusion. I started my formulation career many years after the safety profile of parabens had started to be questioned so am much used to formulating with newer alternatives. Note that parabens are actually banned in some countries specifically for child/infant products.
Formaldehyde Releasing Preservatives
Diazolidinyl Urea is produced by reacting allantoin (a fantastic reparative ingredient) with formaldehyde (a strong fixative/preservative) in the presence of heat and sodium hydroxide. This solution is then mixed with hydrochloric acid and evaporated. A small number of people have contact allergy to these class of compounds and may develop dermatitis because of use. These type of preservatives do not see much use in the UK in skincare products.
Example: Diazolidinyl Urea
PROS
Effective against bacteria
Works in a way to keep the level of free formaldehyde very low in the product
CONS
Poor effect against fungus so needs to be paired
Formaldehyde is not a ‘nice’ chemical that does not have public favour and is a known carcinogen
Are Formaldehyde Releasing Preservatives Safe?
The main safety issues around these class of preservatives is the free formaldehyde that Is generated as the preservative degrades. They are designed to degrade such that the level of formaldehyde in the product is very low but is still an effective anti-microbial. There is not a large amount of data regarding the long-term exposure of individuals to formaldehyde releasing preservatives although formaldehyde itself is carcinogenic. One interesting study showed that the exposure to formaldehyde via cosmetics containing these sort of preservatives is so low that,
The cancer risk from formaldehyde to consumers using FD (formaldehyde donor) containing PC (personal care) products is negligible
While formaldehyde is not a particularly pleasant chemical, the actual exposure to formaldehyde from cosmetics containing these sort of preservatives is incredibly low, far below the suspected cancer-causing concentration. However, potential issues like contact dermatitis do persist.
Organic Acids
An organic acid is an organic compound with acidic properties – a compound capable of donating a proton or forming a covalent bond with an electric pair. In short, when placed in neutral water, acids will lower the pH of that solution. Examples include Lactic Acid, Citric Acid and Malic Acid. All of which can be found commonly in cosmetics and personal care formulations. In the class of preservatives, Sodium Benzoate and Potassium Sorbate are amongst the most widely used organic acids for preservation. Sodium Benzoate specifically is the sodium salt of benzoic acid (an organic acid) and is created by neutralising sodium hydroxide with benzoic acid. It is commonly used as a food pickling agent due to its strong anti-fungal activity. When sodium benzoate is used in cosmetics, it is converted into benzoic acid which is both bacteriostatic and fungistatic.
Example: Sodium Benzoate
PROS
Effective against most moulds/fungi
Seen as safer as they are naturally occurring despite most being made synthetically
CONS
Less effective per weight so more is required compared to other preservatives
Weaker against bacteria
Require specific product pH to work effectively
Can precipitate out of solution
Is Sodium Benzoate (Organic Acid) Safe?
Sodium Benzoate is a common food preservative and is considered safe for consumption both in the USA and UK. Typically, when something is cleared as safe for oral consumption, the assumption is that it is also (but not always) skin safe. As with previous ingredients on this list, rare contact allergies can occur with products that contain Sodium Benzoate but otherwise it is considered a safe and widely used cosmetic preservative. When assessing your products for preservatives it is important to note that Sodium Benzoate is rarely, if ever, used on its own. It usually needs another preservative that is stronger against bacteria to create a well-preserved formula.
Phenoxyethanol
Phenoxyethanol is a very popular ‘newer’ preservative that has gradually replaced paraben and formaldehyde-releasing preservative use in the UK over the last few decades as, overall, it is considered safer. It appears as a colourless, largely scentless, oily liquid that is water soluble. Phenoxyethanol is an organic compound that exists in nature in some plants, but it is synthetically produced for the cosmetic industry where it is often described as a ‘natural mimetic’. Phenoxyethanol is often paired with Ethylhexylglycerine which works to improve the efficacy of Phenoxyethanol by interfering with bacterial cell surface membranes.
It is very useful as it has broad spectrum anti-microbial activity, so depending on the formula, may not need another preservative to fully protect a product although it can be paired with an organic such as Potassium Sorbate for even greater protection. It is effective against yeasts and many forms of bacteria and has a comparatively weak negative effect on the skin’s natural flora. The EU imposes a 1% limit on this preservative and typical formulas will see the concentration anywhere from 0.5%-1%. As of writing it is considered a very well tolerated preservative and is non irritating at recommended use levels however, as with most preservation chemicals, it is not without some drawbacks.
Example: N/A
PROS
Can be considered ‘milder’ than parabens
Effective against many microorganisms
Very stable and not pH dependent
Non-irritating
CONS
Potential issues with use in infants – avoid in these formulas
Is Phenoxyethanol Safe?
Phenoxyethanol is a well-tolerated and effective preservative however in recent years some caveats to its use have emerged. It has been re-assessed on numerous occasions and while it is still considered perfectly safe for use in older children and adults, restrictions and recommendations have been put in place for infant formulas as there are some concerns around liver toxicity and other poorly investigated issues. The consensus in the literature seems to be that phenoxyethanol may be an issue in infants and there is such a small amount of current data that more studies are needed in this area. For this reason, I do not use phenoxyethanol in products designed for children under 10 but it remains my most used preservative for all other categories, usually paired with Potassium Sorbate.
What happens if I don’t use the correct preservative or not enough preservative?
Formulas which are not fully protected via the use of correct preservative combinations or ones which simply do not have enough preservative will ultimately fail before their well-preserved counterparts. This failure typically presents as colour changes, unpleasant smells and visible growth of bacterial slimes and moulds. Even well-preserved formulas can occasionally fail due to things like incorrect storage, expired raw ingredients, contaminated raw ingredients. This is more likely to occur at the development stage before formulas have been through a testing process known as PET – Preservative Efficacy Testing in which the proposed formula is inoculated with common micro-organisms and assessed over several weeks.
There has been large growth in the ‘clean beauty’ sector and while no one can seem to agree what the term ‘clean beauty’ actually means, the original idea was founded on good principles which was to avoid formulating with ingredients that are known to cause human health issues. The problem however is that this notion has now started to be taking too far with many ingredients avoided and bad mouthed by emerging clean beauty brands with no real scientific consensus as to why. Good formulas are SAFE and EFFECTIVE formulas so by attempting to be as clean as possible, some products are poorly preserved leading to contamination and recalls – this is inherently dangerous and surely the opposite of what the clean beauty movement is trying to achieve.
The goal for all formulators should be to create safe and effective products with an accurate anticipated shelf life that allows then to be sold as part of the business ecosystem. This requires shelf lives of multiple months, not days or weeks. You simply can’t do that without good quality preservative ingredients.
Brands which put too much emphasis one what their products DON’T contain (i.e. preservatives) can fall foul of this clean beauty hubris.
KOSAS Alleged Mould in Clean Concealer
JVN Alleged Mould in Scalp Hair Oil
Summary
Cosmetic preservatives come in many forms with different safety profiles, targets, and general efficacies. The key is to balance skin safety with preservatives that are effective. The most effective preservatives are Synthetic or Nature Identical. Natural preservatives can be effective but typically require much higher concentrations in a formula which made lead to its own set of issues. Avoiding preservatives or trying to rely on novel natural preservatives with poor efficacy profiles can lead to contamination of products which is itself inherently unsafe and very damaging to a brand.
· Synthetic, Nature-Identical and Natural Preservatives are available
· They protect against different organisms
· They differ largely in how effective they are
· Safety concerns are often debated in the literature
This post was written by our Chief Scientist, Dr. Edward Jones
