Cosgard, Preservative, 10 ml

Cosgard is a broad-spectrum preservative for water-phase cosmetics, approved for natural cosmetics to the COSMOS standard. It protects creams, serums, tonics and shampoos against bacteria, yeasts and moulds at a use level from 0.6 %. It is widely used in home and small-batch production because it is easy to dose, requires no special processing and works within the typical pH range of skin-care formulations.

The efficacy is provided by a combination of benzyl alcohol and dehydroacetic acid. Benzyl alcohol acts primarily against bacteria, while dehydroacetic acid adds protection against moulds and yeasts. A single preservative thus covers the full spectrum of microorganisms a cosmetics manufacturer typically encounters. The blend contains no parabens, formaldehyde or its donors, EDTA or PEG, and is readily biodegradable.

Key properties

• Broad spectrum of action – effective against bacteria, yeasts and moulds, so in most formulations there is no need to combine multiple preservatives.
• Natural cosmetics – the preservative is COSMOS Approved and vegan, making it suitable for products prepared according to natural certification standards.
• Low use level – the recommended range is 0.6 – 1 %, which in typical formulations means 6 – 10 g per kilogram of product.
• Simple processing – the liquid is added to the finished product during cool-down, without dissolving or heating.
• Rinse-off and leave-on products – suitable for products that are washed off as well as those that remain on the skin.

Use in formulation

The preservative is added in the cool-down phase at a temperature below 80 °C, together with other heat-sensitive ingredients. It dissolves in alcohol and glycols, and only partially in water. In emulsions it disperses without problems at a use level up to 1 %. In clear aqueous products such as tonics or hydrolat sprays, pre-disperse it in a small amount of glycerin, propanediol or ethanol before adding to the water phase to prevent haziness.

The decisive parameter is the pH of the finished product. The preservative works reliably in the range of pH 3 – 6, where dehydroacetic acid is in its effective, undissociated form. Above pH 6 its efficacy declines and protection relies on benzyl alcohol alone. The pH is therefore adjusted before or immediately after adding the preservative and always verified in the finished blend.

The blend is compatible with anionic, amphoteric and non-ionic surfactants, so it can be used in shampoos, shower gels and other wash-off products with pH in the recommended range. For products with a higher content of proteins, starches or botanical extracts, the dose is chosen at the upper end of the range.

Suitable for products such as

• Facial and body creams, lotions and balms with an aqueous phase
• Serums, moisturising gels and tonics
• Shampoos, conditioners and hair masks
• Shower gels, foams and intimate hygiene products
• Children's cosmetics with an aqueous phase, provided pH and dosage are observed
• Decorative cosmetics on a water or emulsion base

The preservative is not added to anhydrous products (massage oils, balms, body butters). They lack the water in which microorganisms would grow.

Good to know

Benzyl alcohol is among the skin allergens that must be listed on the label according to the cosmetics regulation when their content exceeds the specified limit. At the recommended dosage of Cosgard this limit is practically always exceeded, so Benzyl Alcohol is included in the ingredient list on the packaging. This fact is also taken into account when assessing the safety of the product for sensitive skin.

The preservative has the characteristic, slightly sweet scent of benzyl alcohol. In fragranced products it is undetectable; in unscented cosmetics it may be faintly perceptible at a 1 % use level. The brown colour of the raw material does not show in the product at typical use levels; with completely white or clear products it is worth testing a small sample first.

The efficacy of preservation in a specific formulation is verified by a challenge test. For products intended for sale this test is part of the safety assessment report. For home use, at least monitor changes in scent, colour, consistency and appearance of the product during the first weeks of use.

Frequently asked questions