Antimicrobial potentiators are cosmetic materials that have weak activity on their own but work synergistically with known preservatives. They can be very useful in reducing the preservative level in formulations, and they typically provide other useful benefits, as well. Here, I’ll explore product resources for the classes of potentiators, which include chelators, polyols/diols, ethers, and esters. In general I don’t suggest using more than 2% polyols/diols, ethers, and esters in formulations due to potential skin irritation.
Chelators work by binding trace metals like iron, which are needed for survival by microorganisms. They also are useful in helping to prevent formulation discoloration and oxidation. In shampoo formulations, they can improve foam and prevent hard water bathroom deposits.
- Disodium EDTA (EU) by Dow Chemical.
- Sodium Phytate (EU) by Deckner Consulting Services LLC (EU) is a naturally derived chelant that is an excellent replacement for Disodium EDTA. It has been shown to help moisturize skin and normalize sebum in both dry and oily skin types. Improved skin lightening is also claimed.
- Dissolvine G-47-S (glutamic acid, n.n-diacetic acid, tetra sodium salt) is a biodegradable chelant by Akzo Nobel.
- Trilon M (methylglycinediacetic acid trisodium salt) is a biodegradable chelant by BASF (EU).
- Baypure CX 100 (iminodisuccinic acid tetra sodium salt) is a biodegradable chelant by Bayer Material Science.
- MP Diol (Methylpropanediol) by Lyondell is made by fermentation and considered to be a naturally-derived alternative to propylene glycol (EU).
- Hydrolite 5 (EU) (Pentylene Glycol) by Symrise (EU) is claimed to reduce emulsion particle size and help improve stability and formulation aesthetics.
- Hydrolite 6 (EU) (1, 2 Hexanediol) by Symrise has broad spectrum antimicrobial activity of .6-2.5%. It is also one of the best solvents I have evaluated for helping to solubilize oils into water.
- Purolan OD (EU) (Caprylyl Glycol) by Lanxess Distribution (EU).
- Symdiol 68 (EU) (1, 2 Hexanediol and Caprylyl Glycol) by Symrise is a synergistic diol mixture that significantly boosts the antimicrobial activity of preservatives. Symdiol 68 at .5% in a finished formulation was also clinically shown to be comparable to 3% glycerin for skin hydration (Corneometer) and better at reducing TEWL.
- Symdiol 68T (EU) (1, 2 Hexanediol, Caprylyl Glycol, Tropolone) from Symrise is claimed to be a synergistic blend.
- SymClariol (EU) (Decylene Glycol) by Symrise has broad spectrum activity from 500-1000 ppm. It has also been shown to reduce sebum (30% after 28 days).
Ethers are an interesting class of materials due to their excellent stability at low and high PH. Ethers act as solvents to promote the penetration of preservatives into bacterial cell walls.
- Sensiva SC 50 (EU) (Ethylhexylglycerin-Schulke (EU)).
- Sensiva SC 10 (EU) (Ethylhexylglycerin, Caprylyl Glycol-Schulke) by Schulke has better antimicrobial activity and moisturization activity claimed versus Symdiol 68.
Esters act as solvents to promote the penetration of preservatives into bacterial cell walls. They can have hydrolytic stability problems, so I recommend formulating them at a PH of around 6-7.
- Colonial Monolaurin (Glyceryl Monolaurate – 90% mono).
- Capmul 907P (Propylene Glycol Heptanoate) by Abitec.
- Capmul 908P (Propylene Glycol Caprylate) by Abitec.
- Capmul 708G (Glyceryl Caprylate) by Abitec.
Correction: In the original publication of this article, the product MP Diol was improperly attributed. MP Diol (Methyl Propandiol) is produced by Lyondell and not Dupont Tate & Lyle Bio Products. Zemea (Propanediol (EU)) is made by fermentation and considered to be a naturally-derived alternative to Propylene Gycol. Both have been used as preservative potentiators.
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