The Challenges of Formulating with Natural Preservatives

By Lou De Mers, NOW R & D

The use of cosmetics is not a modern phenomenon. Ancient Egyptian women used kohl to darken their eyelids, and Cleopatra is said to have bathed in milk to whiten and soften her skin. More than 3,000 years ago Greek women used poisonous lead carbonate to achieve a pale complexion. NOW formulators in this modern age are adding to this tradition by scientifically developing the most effective natural cosmetic preservative systems in order to provide natural personal care products that people can safely use.

Preservatives perform an important function in cosmetics preparations and are an indispensible ingredient. One of the most important things to remember is that a cosmetic product must be safe for use. Any product manufactured without a preservative to prevent and control microbial growth will start to grow organisms, some of which may be potentially dangerous. A variety of undesirable organisms including yeasts, fungi and bacteria such as E. coli, pseudomonas, staphylococci and streptococcus have been identified in cosmetic preparations. Microbial contamination can also lead to product instability such as product separation, discoloration, and formation of gasses and odors.

Microbial contamination of a cosmetic product can occur in numerous ways: if the customer usage and storage of cosmetics and skin care is lax; by care not taken in replacing lids; using unwashed fingers to remove and apply a cream or lotion from the container; storage in the bottom of a handbag or the glove compartment of the car or in a damp bathroom cupboard. All these create potential breeding grounds for bacteria of all kinds.

Preservation is especially important in moist all-natural products that can serve as a growth media for bacteria and molds if not protected by ingredients that act as preservatives to inhibit that growth and help stabilize a cosmetic product. There is a downside to some preservatives, since in susceptible people they can cause allergies, dermatitis, and other side effects. Certain ones work only in specific conditions, such as a low pH (high acidity).

The important word regarding preservatives is "balance"; with enough preservative necessary to control microbial growth, yet not too much so as to cause reactions or side effects. One such evaluation called AET or Antimicrobial Effectiveness Testing will aid in determining if this balance has been achieved. At NOW Foods we use this method to assure preservative effectiveness.

While certain synthetic preservatives such as the parabens are relatively mild to the skin, certain others, such as formaldehyde donors, are not. In any case, at NOW we wish to avoid the use of such synthetics in our cosmetics and instead are focused on the use of natural and naturally derived preservatives.

One such commonly used preservative is Citricidal®, derived from Grapefruit seeds. Obtained by the chemical modification of Grapefruit seed extractives, it is an extremely effective preservative but also very acidic and can be harsh to the skin. Because of this harshness, we have launched on an ambitious project to develop a primarily natural preservative system that is both effective and mild to the skin.

Many different preservative candidates have been reviewed. They ranged from essential oils and their components possessing antimicrobial properties to plant extracts, amino acid derivatives and enzymes. The candidates were formulated in our test cosmetic emulsion that is very sensitive to microbial contamination, making it the ideal test medium.

The essential oils Clove, Cinnamon, Origanum and Thyme are known for their antimicrobial properties. These oils, and their major active components, were formulated at various concentrations in our test cosmetic emulsion. Also evaluated in this test emulsion were various citrus plant extracts and Birch extracts. Surprisingly, when subjected to the AET protocol, these all demonstrated either little or no preservative action. The Birch extracts performed poorly as well. The AET protocol calls for a specific reduction, or elimination, of five test microbes and these candidates failed in this respect.

Amino Acid derivatives were also tested. One derivative, specifically Lauric Arginate, showed excellent preservative properties. It functioned well at the 4 – 7 pH range, is very mild, and is all natural. One drawback is it cannot be used with certain ingredients. Another approach was the use of a unique enzyme/ substrate combination. This system was found to be effective in creams, lotions, and oral care products; however it only functions in a 4.0 – 6.0 pH range.
Certain peptides are currently being evaluated with excellent results. They function at a 3.5 – 7.5 pH range, are very mild, and appear to work well with all cosmetic ingredients. The evaluation is currently being expanded to cover a broad cosmetic spectrum, as well as determining synergy with other cosmetic ingredients.

While it was found that there is no one broad-spectrum all-natural preservative, it appears a combination of natural preservatives could be effective when combined with either certain cosmetic ingredients or very mild and safe synthetic preservatives.

At NOW Foods we are spending the time and money on properly developing our cosmetics by tracking the entire manufacturing process to ensure that our products are stable yet not over-filled with preservatives.

Synthetic preservatives known to be allergens or sensitizers that we don’t use at NOW include:

2-Bromo-2-Nitropropane,
5-Bromo-5-Nitro-1,
Acid Ammonium Sulphate
Bromidox
Butylated Hydroxytolulene
Dichlorobenzyl Alcohol
DMDM Hydantoin
Formaldehyde
Imidazolidinyl Urea
Methylchloroisothiazolinone
3Diol 3-Ido-2-Propynl Butyl Carbonate
3Dioxane Benzalkonium Chloride
Butylparaben
Diazolidinyl Urea
Ethylparaben
Isobutylparaben
Methylparaben
Methylisothialinone
Propylparaben
Quaternium-15
Sodium Dehydroacetate
 

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