antibacterial agents is further driving this trend toward
It is worth noting that the use of synthetic preservatives
at their recommended dose levels did not seem to cause any
skin irritation in an analysis of 45,000 human subjects.
While a large number of essential oils are known to possess
antibacterial and antifungal activity, their safety, efficacy,
and stability in formulated cosmetics as preservatives has
been of limited scope. A number of such preservatives contain phenolic or polyunsaturated antimicrobial and antioxidant components, which renders them sensitive to discoloration due to air oxidation (especially in formulations above
pH 8.0 and/or presence of oxidizing metals such as copper,
iron, and nickel.
A few recent examples of essential oil-based preservatives in formulated products are noted here in anticipation of further commercial development of essential oils as
cosmetics preservatives. In this regard, the olfactory and
color attributes of certain essential oils continue to pose formulating challenges as preservatives. The essential oil of
curcumin (Curcuma longa), for example, has shown potent
antibacterial and antifungal activity. The yellow color and
strong medicinal odor of turmeric oil prevents its use as a
natural preservative in cosmetics. Ginger oil has been reported as a good preservative for fish products. The strong,
spicy aroma of this oil, however, does not offer promise for
its use as a cosmetic preservative.
Salva-de-marajó: Plants of Lippia sp. (origanum family) are well known for their aromatic constituents. Lippia
origanoides is a very aromatic shrub distributed from North
America to South America, with prominent occurrence in
the Amazonian region of Brazil, the Guianas, Venezuela,
A recent study on the essential oil of L. origanoides,
which consisted mainly of oxygenated monoterpenes (38%)
and carvacrol (26%), showed that it inhibited the growth of
all the tested microorganisms. The Ames test indicated that
this oil was non-mutagenic. In combination with polysor-bate 80, the essential oil exerted preservative action on orange juice, as well as cosmetic and pharmaceutical compositions, especially in the case of aqueous-based formulations.
West Indian Raspberry (Rubus rosifolius): This
plant is a prickly shrub native to rainforests and forests of
the Himalayas, East Asia, and eastern Australia. The extract of this plant was evaluated as a preservative at 0.2%
(w/w) use level in two different base formulations (emulsion
and gel). The microbial challenge test was performed with
the standardized microorganisms. The results demonstrated the extract reduced the bacterial inoculate. However, it
was not an effective preservative against fungi, thus requiring a complementary antifungal agent.
Self-Preserving Cosmetics: An emerging trend of
self-preserving and preservative-free cosmetics is on the
horizon. This feat is achieved by using a combination of
antioxidants, chelating agents, and bioactive essential oils.
Phenethyl alcohol, an essential oil component of rose oil, in
combination with caprylyl glycol and glyceryl caprylate, is
a new preservative for emulsion formulations, especially
those of droplet particle size in the range of 100-900 nm.
A design space model for preservative optimization, developed for synthetic preservatives, may be applicable for natural ingredients-based cosmetic preservatives.
The future of self-preserving and preservatives-free
formulations is of limited practicality due to a plethora of
reasons, including limited availability of natural preservatives with proven broad-spectrum efficacy at low (0.1-0.5%)
use levels, the complexity of additives and ingredients in a
formula, pH ranges, stability criteria, activity against mutations of resistant bacteria, and regulatory requirements
of such formulations.
The formulation of essential oil-based massage oils requires
a prudent selection of essential oils and other emollient ingredients for their consumer acceptance, skin safety, and
sensorial attributes. The application of essential oils for
preservation of cosmetics replacing synthetics is still in its
The use of seed oils for massage requires a careful selection of such oils. Oleic acid, among all other fatty acid
constituents of seed oils, has been shown to penetrate skin
the most. This may explain why olive oil causes dermatitis
on topical application. The oils that are high in oleic content
(C18-1) need discretion for massage applications.
The technologies for preservative-free cosmetics are envisioned to be of limited applicability due to the variety of
ingredients used in such formulations. The mutations of
bacteria resistant to synthetic and other preservatives in
cosmetics formulations shall pose additional challenges for
preservatives-free cosmetics research. n
For references visit the online version at
Nutraceuticals World.com and Happi.com.
About the author: Shyam Gupta is an international consultant
in innovative topical and skin care formulations based on new
ingredients and delivery systems with over 100 patents, patent applications, cosmetics publications, and book chapters. He
specializes in consumer-desirable, nature-based ingredients with
incomparable efficacy and performance attributes. For more
information: 602-996-9700, E-mail: email@example.com,