The use of essential oils in the production of cosmetics and related products may have several advantages, such as enhancing the dermato-cosmetic properties and preservation, as well as the marketing image of the final product. The use of botanical materials such as essential oils in cosmetic formulations at relatively high concentrations is likely to provide skin benefit. The potential of essential oils indigenous to the tropical and subtropical part of Africa has not been sufficiently exploited in this regard. Using a challenge test, this study demonstrates the potential application of two South African indigenous plant essential oils, viz. Artemisia afra and Pteronia incana oils, and oils of two Mediterranean aromatic plants grown in South Africa, viz. Lavandula officinalis, and Rosmarinus officinalis, to be used as natural cosmetic preservatives in an aqueous cream formulation. Except for Pseudomonas aeruginosa strains, the oils displayed remarkable antimicrobial activities against all common test organisms (including bacteria and fungi) and environmental isolates used. All the test microorganisms used in this study were generally more susceptible to the oils during the challenge test in aqueous cream compared to the antimicrobial test performed on agar. The results indicate, therefore, that the oils can be recommended as candidate natural cosmetic preservatives. Artemisia afra oil was the most efficient in reducing the load of artificial contaminations in the aqueous cream formulation within 2-7 days. Since relatively high concentrations of the oils were used, the oils could at the same time serve as natural fragrances in aqueous cream, in addition to assuring protection against microbial contamination.