K. von Nessen, F. Weiher, M. Neubauer, T. Kerl, J. Preuschen
In recent years the demand from consumers for natural preservation systems for personal care products has increased significantly.
Since many preservatives are not sufficiently effective against all microbes when used alone, more and more often a combination with preservation boosters such as 1,2-hexanediol is required. One well-established natural preservative is lactic acid, which is known to reduce bacteria in aqueous systems. In this study, preservation stress tests according to the European
Pharmacopeia (Ph. Eur. or EP) were carried out for single ingredients and combinations of lactic acid with 1,2-hexanediol in an aqueous solution of sodium laureth sulfate (SLES) as a basic system.
Sufficient preservation of the basic system could not be achieved with the individual substances alone. In contrast, in combination the two showed a synergistic effect and the test was passed. This synergistic effect of the combination of lactic acid and 1,2-hexanediol was verified in a shower gel formulation.