Preservatives in skincare products may negatively affect cells via impact on collagen: New study

Cosmetic products typically contain preservatives to prevent microbial growth but the types of preservatives in skincare products have reportedly led to side effects when applied on the skin. Researchers at the Medical University of Lublin in Poland tested a range of such preservatives in order to determine how preservative concentration, cell growth, collagen secretion, and cell viability were linked.

The preservatives tested included phenoxyethanol, methyl paraben, propyl paraben, imidazolidinyl urea (IU), the composition of gluconolactone and sodium benzoate (GSB), diazolidinyl urea (DU) and two grapefruit essential oils. One of the grapefruit oils was industrially produced and the other was freshly distilled from fresh grapefruit peels.

The researchers then hypothesized that these preservatives caused “a decrease in collagen secretion from human dermal fibroblasts”.

Skin in the game

As the most widespread structural protein in the human body, collagen forms molecular structures that strengthen tendons and elastic fibres that support the stability of skin structures, numerous tissues and internal organs. Its key mechanical properties are high levels of elasticity and tensile strength.

The researchers screened the examined compounds in vitro for anti-bacterial and anti-fungal activities and found that while they possessed these properties, some of them also appeared to lower collagen concentration.

Methyl paraben, for instance, was found to have induced a decrease in collagen concentration through reduced collagen synthesis. This was of particular concern as parabens possess advantageous properties that have led to their wide application in cosmetics, pharmaceuticals and food products. However, recent studies (such as this one) have “uncovered their ability to accumulate in tissues and exert many adverse effects”.

The study also observed that despite their potential anti-microbial activity, “the most destructive influence of preservatives on collagen synthesis was observed in the case of IU and DU”. The freshly distilled homemade grapefruit oil, on the other hand, turned out to have the mildest effects on the same process.

These results may have positive implications for cosmetics and skincare product manufacturing, as the current market trend is focused on using natural ingredients, including extracted substances from plants, like essential oils.

Still, essential oils in such products present their fair share of challenges, such as high volatility, low chemical and thermal stability, and low water-solubility. For this reason, new research is looking into the encapsulation of certain essential oils in nanocarriers, which could “eliminate most of the difficulties and spread natural substances in everyday usage”.

The researchers noted that based on the study’s results, both natural and synthesized compounds “require controlled use” and that more aspects beyond appropriate dosages and the evaluation of preservative efficacy should be considered. They added that the “complex effect of preservatives on skin processes and cytotoxicity is an important topic for modern people”.

Limitations and future indications

In addition to the aforementioned findings on the effects of certain cosmetic preservatives on collagen synthesis and secretion, the researchers acknowledged the study’s limitations. For one, the viability test they had used (MTS assay) was only a preliminary test; they stated that “proliferative market measurement experiments could be beneficial in a broader assessment” and would certainly provide “more complex conclusions”.

They added that in this study, they had experimented on a large group of compounds and as such, wanted to conduct more detailed research on selected compounds in future; this would allow them to determine which compound had the “most promising application.

Source: Cells

https://doi.org/10.3390/cells12071076​

“Effect of Commonly Used Cosmetic Preservatives on Healthy Human Skin Cells”

Authors: Patrycja Głaz, et al.