I doubt I'm the only one who was utterly revolted by Marta's photo of her moldy 6-month-old conditioner.  Clearly, citric acid and rosemary extracts didn't cut it in the preservative department.  So, how can you avoid parabens and other nasty preservatives without finding fuzz on your favorite products?  Without further ado, here is a round-up of nature's most effective preservatives.

Vitamins A (retinyl), C (ascorbic acid), and E (tocopherol) all help slow down the natural oxidation process, keeping oil-based applications fresher for longer periods and prolonging their shelf life before they go rancid.  Any products that contain a large amount of oil, such as ointments, massage oils, and bath salts, need an antioxidant to prevent them from breaking down and losing their potency.  Vitamins A, C, and E also protect skin cells from the damaging effects of free radicals.  Do not be fooled by the synthetic version of vitamin C on the market, which goes by a number of aliases such as Alpha Tocopherol and Tocopherol Acetate.  Vitamin E is preferable, since certain forms of vitamin C can be unstable.

Because honey is bound by high levels of sugar, an organic compound that acts as a preservative, it can protect cosmetic products from spoilage.  Microorganisms are unable to grow in honey due to its low moisture content and low pH.  A natural anti-microbial and antibacterial, honey is also an excellent moisturizer.  Honey's humectant properties retain moisture in the skin.  Similar to honey, neem oil and sweet orange oil are also mild but effective natural preservatives capable of killing both bacteria and fungi.

Technically speaking, grapefruit seed extract cannot be considered a truly natural preservative, since it is manufactured out of grapefruit pulp by-product and is thus a chemically altered form of grapefruit seed.   Not to be confused with grapefruit essential oil or grapefruit oil (a carrier oil), grapefruit seed extract has shown high growth-inhibiting activity against germs in lab tests.  It is reportedly effective against more than 800 bacterial and viral organisms and 100 strains of fungus.  Well-tolerated by the skin, .5% to 2% (3 to 12 drops) should be sufficient for 1 oz. of cream.

Essential oils are natural substances derived from flowers, leaves, and woody plants.  During the cholera epidemics in the 19th century, it was discovered that perfume factory workers survived the disease almost entirely unscathed because the essential oils that they handled acted as antiseptics.  Though cosmetic formulations do not often depend on them for preservative power, essential oils can kill harmful bacteria and fungi, as well as heal affected skin, without jeopardizing the immune system.  Studies in France determined the potency of various essential oils by adding them to raw meat stock cultured in sewage (yum).  The results indicated that the minimum concentration needed to kill all microbes was .9% for violet, .7% for lemon, .6% for juniper, .5% for lavender, .4% for cinnamon, .25% for peppermint, and .2% for clove.   Sweet orange and thyme were the most effective at .12% and .07% respectively.  An unfortunate consequence of high concentrations of essential oils is skin irritation and dermatitis, still preferable to some of the adverse side effects of synthetic preservatives.

There have been some promising developments in the lab to isolate and synthesize natural ingredients that convey preservative power.  Biopein and Neopein are both blends of herbal extracts that are very effective preservatives.  In clinical trials conducted by the manufacturer, these agents proved to match or exceed the performance of commonly used synthetic preservatives.  Another natural option is Naturagard, a patented fatty acid ester derived from 100% vegetable sources and Eco-cert certified.  This skin-conditioning agent can be used in "self preserving systems" for cosmetics since when combined with lactic acid to adjust the pH, it is just as effective as phenoxyethanol and methylparaben.  Unlike herbal blends, Naturagard is colorless and odorless.  Lastly, a company in Germany called Dr Straetmans has developed a plant-based fungicidal ingredient, Dermosoft 688 ECO, which has been proven to provide complete protection from microbiological deterioration.

Although using these natural preservatives will stave off the growth of microorganisms in the short term, their limited potency won't achieve the shelf life of 2+ years in most mass market products.  They will, however, abstain from introducing carcinogenic toxins into your body.  You can expect to get up to a year's worth of use out of oil-based serums, balms, butters, and perfumes.  But for any water-based products, such as creams and lotions, use immediately and store in a cool place (not a humid bathroom- the ideal environment for growing just about anything).