Phenoxyethanol in skin care is used as a preservative. Although the kind of phenoxyethanol used in skin care is synthetic (known as “nature identical,” it mimics the natural version exactly), phenoxyethanol is actually found in nature, specifically in green tea and chicory. It makes sure yeast, mold, and bacteria don’t develop and ultimately, end up on your skin!

Technically, phenoxyethanol forms via a reaction between phenol (EU) and ethylene oxide (EU). Aside from acting as a preservative, it’s even been used in vaccines. Chances are, many of the products you use include it as it’s one of the most popular skin care preservatives in use. You’ll find phenoxyethanol in everything from eye creams to moisturizers, so it’s a good idea to understand what it does and doesn’t do.

Is phenoxyethanol safe?

Yes, phenoxyethanol is safe. According to the Cosmetic Ingredient Review, when used in concentrations of 1% or less, phenoxyethanol in skin care is safe. This is also the same standard the European Commission on Health and Food Safety uses as well.

As phenoxyethanol has become popular as a cosmetics preservative in the last few years, there’s been some debate as to its safety. Although there are some opinions that differ (we’ll get to that in a sec), the general consensus is that phenoxyethanol is safe in skin care, as long as it’s used in concentrations of 1% or less. Many of the studies that have been published in which phenoxyethanol is found to be an irritant, are doing so in reference to much larger concentrations.

Think of it this way: carrots are wonderful for you--full of potassium, vitamin C, and all kinds of other great things. That said, if you eat too many of them, your skin can turn orange (literally--it’s a thing!). That’s kind of how phenoxyethanol works. In small concentrations of 1% or less, it’s incredibly beneficial, in enormous quantities over long periods of time, it could cause some issues. The truth is, no ingredient, no matter how natural or free of chemicals , can be completely ruled out as an irritant on the skin of every single person on the planet.

The main thing to remember is that any study that considers phenoxyethanol as a preservative using more than a concentration of 1%, isn’t really applicable (like a study that concludes carrots are bad for you if the researchers based it on someone eating 200 carrots a day).

That said, what is agreed, is that phenoxyethanol should not be ingested by babies or children under three years old, so make sure not to apply any skin care products with phenoxyethanol on areas of the body where a baby might suckle or even lick the skin.

What do Preservatives Do?

Preservatives in skin care prevent the growth of yeast, mold, and bacteria. Just like food, skin care, make-up, and fragrances all have a certain shelf life and without some kind of preservative, that shelf life would be very, very short (especially since most skin care and cosmetic products contain a lot of water, an environment in which mold thrives). Sans preservatives, you’d be putting the equivalent of moldy bread on your face every day. If you don’t believe us, put together a little DIY scrub and see what happens after a few days. We’re willing to bet it’s not something you’d want to use!

Introduction

Antiseptics have been used in clinical and domestic applications for over half a century. Nowadays, the use of antiseptics and disinfectants is questioned, because chronic exposure to such agents can have deleterious effects on human health and can select for less susceptible strains towards biocides and antibiotics (Lin and Hemming 1996; Braoudaki and Hilton 2004). Among cationic antimicrobial agents, quaternary ammonium compounds (QACs) like benzalkonium chlorides and biguanides like chlorhexidine have different behaviour. The biguanides differ from other cationic biocides in that they interact only superficially with the lipid bilayer altering fluidity through cation displacement and headgroup bridging (Chawner and Gilbert 1989). QACs on the contrary interact fully with the membrane and are therefore susceptible to resistance mechanisms mediated through multidrug efflux pumps (Lambert and Hammond 1973; Heir et al. 1999). QACs can cause various degrees of occular and dermal irritation (Lin and Hemming 1996), whereas the toxicity profile with regard to skin irritancy and hypersensitivity of biguanides is excellent at typical in-use levels (Tupker et al. 1997).

Bacteria inside biofilms have increased resistance to antimicrobial agents (Gilbert et al. 2001; Saginur et al. 2006). The biofilm effect onto bacterial resistance is thought to be related to a direct role for the exopolymeric matrix as a diffusion barrier, to a chemical reaction of some chemicals with the biofilm matrix and to physiological differences between fixed and suspended organisms (Mah and O’Toole 2001; Russel 2002). It might be interesting to develop preventive treatments that could inhibit biofilm development to prevent from this biofilm-related antimicrobial resistance. Several studies in the literature have examined prevention of plaque formation in the presence of chlorhexidine (Van der Weijden et al. 2005; Chin et al. 2006; Featherstone 2006; Modesto and Drake 2006). Other studies assessed the activities of chlorhexidine bladder washout procedures in the treatment of urinary tract infections in patients with indwelling catheters (Stickler et al. 1987; King and Stickler 1992). QAC coatings on different surfaces have been shown to be effective in preventing microbial biofilm formation (Nikawa et al. 2005;Mangalappalli-Illathu and Korber 2006; Oosterhof et al. 2006). In the present work, we have investigated whether the biofilm formation of some reference strains of opportunistic human pathogens can be influenced by two cationic antiseptics, benzalkonium chloride and chlorhexidine, at in-use and sub-minimal inhibitory concentrations (sub-MICs).

Materials and methods

Bacterial strains

Four bacterial strains of opportunistic human pathogens were used in the present study: the uropathogenic Escherichia coli G1473 (Di Martino et al. 2005), hospital Klebsiella pneumoniae CF504 (Di Martino et al. 1995), reference Pseudomonas aeruginosa PAO1 (CIP104116) and Staphylococcus epidermidis CIP53124 strains have been purchased from the catalogue of strains, ‘collection de l’institut Pasteur (CIP),’ Institut Pasteur CIP, Paris, France.

Antiseptics

The antiseptics used in the present study were chlorhexidine diacetate (Fluka, Buchs, Switzerland) and benzalkonium chloride (Sigma-Aldrich, L’Ile d’Abeau, France). Standard MICs were determined by broth microdilution in three unrelated experiments. Briefly, 50?μl of bacterial suspension containing 2?×?106?CFU?ml?1 in Tryptone Soya (TS) medium (Sigma, Saint Quentin Fallavier, France) were added to 50?μl of serial twofold dilutions of the disinfectants in TS in microtiter trays. The plates were incubated for 24?h at 37°C and observed for turbidity. The MIC was defined as the lowest concentration of antiseptic, inhibiting visible bacterial growth.

Biofilm assay

The biofilm formation assay was done in 96-well microtiter dishes made of polystyrene (Sero-wel; Bibby Sterilin Ltd, Stone, Staffordshire, UK) as previously described (Di Martino et al. 2005). Bacterial cells of overnight cultures at 37°C were resuspended at optical density, OD620?nm?=?0·05 in TS broth supplemented with or without the antimicrobial agent at different concentrations. Plates were inoculated with the bacterial suspensions (100?μl per well) and incubated at 37°C for 24?h. The planktonic growth was determined by measuring the absorbance at 620?nm. After thorough washings with water, 100?μl of crystal violet (1%) was added to each well, the plates were incubated for 30?min at room temperature, rinsed thoroughly and repeatedly with water, the dye was solubilized in SDS 1% (100?μl per well) and the absorbance at 595?nm was determined. Each result represents the mean of at least three separate experiments.

Silver ion antimicrobial technology is a silver-based active ingredient that can be incorporated into polymers, coatings, textiles and more to offer continuous product protection against bacterial growth.

Chlorphenesin

Chlorphenesin is a synthetic compound that belongs to the class of organic compounds called organohalogens. Chlorphenesin is a phenol ether (3-(4-chlorophenoxy)-1,2-propanediol), derived from chlorophenol containing a covalently bound chlorine atom. Description of this cosmetic preservative by Expertox.