Preservation and format

In brief

Every water-based serum needs a preservative system, and every NanoSerum has one: a minimal preservative system built from multifunctional ingredients. The sealed vial format reduces how much work that system has to do in use. It is one part of the approach set out on the Technology hub.

Why every water-based serum is preserved

Water supports microbial life. A serum that contains water will, sooner or later, meet bacteria, yeasts or molds: from the air, from fingers, from an applicator dipped back into the pack. A preservative system is there to stop anything that gets in from multiplying across the whole period the product is in use.

"Preservative-free" water-based products do exist. They depend on single-portion packs, specialist packaging, or a formula hostile to microbial growth for other reasons, such as very low water content. The idea that no preservative is always gentler is examined on Natural is gentler.

What the format changes

The risk a preservative system faces depends on how the product is used. An open jar is touched by fingers and exposed to air every day. A dropper bottle is opened each time and the pipette returns to the bottle. Each of these puts new microorganisms into the product with every use.

The sealed vial format removes most of those routes. The vials and stoppers are sterilized before filling. Each vial is filled and sealed immediately under a butyl stopper and a 20 mm aluminum crimp with a flip-off cap. The serum is a preserved cosmetic formulation. Each dose is drawn through the stopper with a syringe, and nothing is ever returned to the vial. After the first draw, the vial is refrigerated and used within 28 days. Handling rules for the treatment room are on Vial handling.

ISO 29621 describes how packaging that prevents contamination in use lowers a product's microbiological risk. The format works alongside the preservative system and narrows the job it has to do.

What the formulas use

Each formula's preservative system is declared in its ingredient list. In the Hyaluronic Skin Repair NanoSerum, the system is built from 1,2-hexanediol and ethylhexylglycerin, multifunctional ingredients that also contribute to how the serum feels, with disodium EDTA as a chelating agent. The same formula is free from parabens and formaldehyde donors.

Systems differ by formula. The Hydrating NanoSerum adds caprylyl glycol. The Scalp Repair NanoSerum adds caprylhydroxamic acid, and alcohol is its second ingredient. Each product page carries its full ingredient declaration, in descending order.

How preservative efficacy is measured

ISO 11930 is the international standard for evaluating the antimicrobial protection of a cosmetic. It is a challenge test. The laboratory introduces a defined set of microorganisms into the product: two bacteria associated with skin and water, a gut bacterium, a yeast and a mold. It then counts how many survive at fixed intervals over several weeks. To pass, the counts must fall by set amounts within set times. Criterion A is the stricter pass; Criterion B is accepted when the packaging or use pattern adds protection and a risk assessment supports it.

How Vegalab grades evidence is on How we test. The finished-product tests for preservation and microbial quality are explained on the Testing program.

Two formats

Most formulas are also sold in a bottle, such as the Hyaluronic Skin Repair NanoSerum 30 ml, formulated separately from the sealed vial set. The vial set adds the in-use protection of a pack that is never opened to air.

Preservation protects the formula from microorganisms. Protection of the active from oxygen, light and pH is a separate job, covered on Stability and protection. For the in-use period of an opened vial, see How long does an opened vial last?. Terms are defined in the glossary.

References

1. International Organization for Standardization. ISO 11930:2019 Cosmetics: Microbiology: Evaluation of the antimicrobial protection of a cosmetic product.
2. International Organization for Standardization. ISO 29621:2017 Cosmetics: Microbiology: Guidelines for the risk assessment and identification of microbiologically low-risk products.