Cold plasma and cosmetics / Article 08
Cosmetics that want to cut back on preservatives: where plasma-activated water sits in a formulation
For brand owners and contract manufacturers developing clean-label formulations — the mechanism, the limits, the criteria a formulation still has to pass, and the registration route.
Plasma-activated water in a cosmetic formulation works as one layer of the preservation system. It is not a single preservative replacing everything that was there before. The principle is to combine several mechanisms so the formulation passes microbiological safety criteria while relying less on the preservative groups consumers avoid.
The first thing to be clear about: a formulation without conventional preservatives still has to pass exactly the same criteria. ISO 11930 and USP 51 have no relaxed standard for clean-label products. Marketing can change; the criteria do not.
This article explains how the mechanism works, what is genuinely achievable, what still has to be proven, and how a project of this kind should run.
01Why brands want to move away from the conventional preservative groups
The pressure comes from two directions at once: tightening regulation, and consumers who read labels.
On regulation, the European Union banned methylisothiazolinone in leave-on products in 2017 and limited its concentration in rinse-off products. Several long-chain parabens were banned in 2014, and the total permitted paraben concentration is tightly capped.
On the consumer side, phenoxyethanol remains on the permitted preservative list at up to one per cent, but it has become a name the clean beauty segment avoids, particularly in products for children and for sensitive skin.
So brands have to find another route that still passes the same criteria. There are several, and they usually have to be combined.
| Option | How it works | Limits |
|---|---|---|
| Natural-origin preservatives | Substances with antimicrobial activity from natural sources replace synthetic ones. | The spectrum is usually narrower, and some carry constraints on odour or stability. |
| Organic acids at specific concentrations | Lower the pH and inhibit microbial growth. | Constrains the formulation's pH range, which may not suit some product types. |
| Formulating for low free water | Reduces the water available to microorganisms, making growth difficult. | Only works for certain product formats. |
| Combining several mechanisms | Layers several defences so the combined effect passes. | More complex to design and requires more testing. |
| Plasma-activated water | Reduces microorganisms in the water phase from the preparation stage, and acts as one of the protective layers. | Activity falls off over time, so it has to be generated at the point of use. |
02How plasma-activated water works in a formulation
When cold plasma reacts with water it creates chemically active species in the water with antimicrobial activity spanning Gram-positive and Gram-negative bacteria, yeasts and moulds.
There are two main ways to use it. The first is in-line microbial reduction while preparing the water phase, which lowers the starting microbial load before mixing. The second is as one layer of the preservation system, alongside natural antimicrobials and organic acids, so that the combined effect passes the criteria.
A research team affiliated with TIBD has developed this further into a plasma-activated water integrating lactic acid, a substance the cosmetics industry already accepts both for pH adjustment and for supporting the skin's acid mantle. Combining the two achieves preservation performance at a lower concentration than conventional preservatives alone. The technology is at patent filing stage, covering both the production process and its application in formulation systems.
The limitation to accept is that the activity of the species in plasma-activated water falls off with time and storage conditions. The most workable arrangement is therefore generation in the cosmetics manufacturer's own line, rather than buying it in as a raw material and keeping it in a tank.
03What the research reports
| Study | Journal | What it reports |
|---|---|---|
| Bekeschus et al. (2020) | Scientific Reports | The antimicrobial activity of plasma-activated water is driven by two groups of components acting independently of each other. |
| Boxhammer et al. (2015) | Plasma Processes and Polymers | Cold air plasma significantly reduced populations of Escherichia coli, Staphylococcus aureus and Candida albicans within a few minutes, under specifically designed test conditions. |
| Suwannarat et al. (2024) | ACS Applied Bio Materials | The effectiveness of discharge plasma in liquid against Gram-negative bacteria, used as a model for contamination in formulation systems. |
The caution when reading this group: the reduction figures were measured in controlled test systems, not in a real cosmetic formulation with other ingredients present. A real formulation contains substances that may react, and nutrients organisms can use. Proof therefore has to come from testing the formulation, not the water.
04What the formulation has to pass
The test that decides whether a formulation works is preservative efficacy testing, to ISO 11930 or USP 51.
The method inoculates a sample of the formulation with five reference organisms — Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans and Aspergillus brasiliensis — then counts the surviving population at defined time points, day 7, day 14 and day 28, to see whether the formulation's preservation system reduces them to the required level.
The formulation also has to pass stability testing, both accelerated and long-term under ICH Q1A, and photostability testing under ICH Q1B where the product is exposed to light.
The resulting documentation set comprises the formulation sheet listing ingredients by international nomenclature and concentration, a manufacturing procedure stating the steps, the parameters to control and the in-process testing, stability data, and the preservative efficacy test report. Together, that is what a notification is filed with.
05Why TIBD hands over the formulation to be manufactured rather than manufacturing it
Three reasons
- The activity of plasma-activated water falls off over time. The best-performing arrangement is generation in the cosmetics manufacturer's own line, which favours the brand owner manufacturing rather than outsourcing elsewhere.
- Thailand already has a large number of contract manufacturers certified to good manufacturing practice. Designing for the brand owner to take the formulation into an existing plant adds value across the whole chain without duplicating capacity.
- Rights in the formulation and the right to develop it further are assets the brand owner should hold, so they can manage a long-term product plan independently.
Partners suited to this arrangement are brand owners with in-house R&D and either their own plant or a certified contract manufacturer; upper-tier contract manufacturers wanting to add a technological differentiator for their brand customers; and clean beauty companies wanting a product line with real science behind it.
06The registration route
In Thailand, the Cosmetics Act B.E. 2558 and Thai FDA regulations require the notifier to list ingredients by international nomenclature and to take responsibility for the safety of the product.
In the European Union, Regulation (EC) No 1223/2009 requires every product to have a cosmetic product safety report covering both the safety assessment of the ingredients and of the product itself.
How plasma-activated water is positioned in the formulation can be designed several ways: as a water preparation process carried out before filling, as an ingredient that already has an international name, or in a form requiring a new international name for a specific raw material. That choice affects both the label and the documentation, so it should be decided at the start of the project, not at filing.
At industry standard level, ISO 22716 is the framework the manufacturing plant works to, ISO 16128 is used to declare the proportion of natural-origin components in a formulation, and ISO 11930 is the testing framework regulators worldwide accept.
07In summary: four points before deciding
Four things to remember before deciding
- The pressure comes from two directions at once: tightening regulation, and consumers who read labels.
- Plasma-activated water has antimicrobial activity spanning Gram-positive and Gram-negative bacteria, yeasts and moulds.
- What decides whether a formulation works is preservative efficacy testing to ISO 11930 or USP 51, not a result in a test tube.
- The activity of plasma-activated water falls off over time. The best-performing arrangement is generation in the plant's own line, which is why TIBD hands over the formulation rather than manufacturing it.
08Frequently asked questions
Can a formulation using plasma-activated water be called preservative-free?
It depends what else is in it. If the preservation system still relies on organic acids or natural antimicrobials, the declaration has to reflect what is actually on the label. A label claim must always match the ingredients filed in the notification.
Does the product keep as long as a conventional formulation?
That has to be proven by stability testing like any other formulation. Nothing is assumed in advance. The shelf life stated on the label has to come from real test results for that formulation.
What does the plant have to invest in?
A system for generating plasma-activated water in the line, sized according to the daily water volume. The design is done with the plant's engineering team, and can be arranged as a unit connecting to the existing water preparation system.
Does it work for every product type?
Not every type. Products with a high water phase, such as toners, essences and cleansers, are the best fit. In oil-based or anhydrous products this mechanism has almost no role, so the product type has to be chosen correctly when the brief is set.
Does the whole existing formulation have to change?
The whole formulation does not have to be rebuilt, but changing the preservation system affects stability and pH, so the full test set has to be run again. It is not a matter of swapping one ingredient and reusing the previous test results.
09Talk through your problem with the TIBD team
If your brand wants to reduce the conventional preservative groups but still has to pass ISO 11930, start by talking through where the current formulation is stuck.
TIBD works alongside researchers and technology owners so that research carries on from the laboratory through to a real production line. The first thing we do is assess together whether your problem genuinely suits this technology. If it does not, we will say so at the start.
Message us on LINE @tibdglobal or use the contact form at tibdglobal.com/contact and tell us about the problem in your process.
Read next
- Process waterCold plasma sterilization without adding anything to the water
- Plasma-activated water actives for skincareWhat the research says, and where the line sits
- Cold plasma devices for skinThe line between a cosmetic and a medical device
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Sources Bekeschus et al. (2020) Scientific Reports DOI: 10.1038/s41598-020-65761-1 · Boxhammer et al. (2015) Plasma Processes and Polymers DOI: 10.1002/ppap.201400174 · Suwannarat et al. (2024) ACS Applied Bio Materials · Standards and regulatory framework: ISO 11930:2019, ISO 22716:2007, ISO 16128, USP 51, ICH Q1A(R2), ICH Q1B, Thailand Cosmetics Act B.E. 2558, Regulation (EC) No 1223/2009 · The lactic-acid-integrated plasma-activated water technology is at patent filing stage with a research team affiliated with TIBD · Cold plasma research in Thailand by Assoc. Prof. Dr. Siwapon Srisonphan Kasetsart University
About TIBD TIBD Company Limited works alongside researchers and technology owners so that research carries on from the laboratory into real industrial use, from feasibility assessment and test design to prototyping and scale-up of production, with VISBIO, an affiliated company, acting as the independent verifier. The office is at the Kasetsart Agricultural and Agro-Industrial Product Improvement Institute, Kasetsart University, Bangkhen.