Water activity – aw
Water activity — rated aw — represents the amount of free water available in a cosmetic product. This is water that can be used by microorganisms or involved in physicochemical reactions.
The aw is measured on a scale ranging from 0 (no free water) to 1 (pure water). Unlike total water content, the aw makes it possible to determine the fraction that is actually active in the microbiological, chemical, and physical stability of a formula.
This data is used throughout Europe, particularly in Switzerland, where quality control and safety standards for cosmetics are strictly regulated, both for local brands and for companies exporting to the country.
Importance of water activity for the cosmetics sector
Enhanced microbiological safety
The aw value is one of the most reliable indicators for anticipating and controlling the proliferation of microorganisms. Controlling water activity significantly reduces the risk of contamination in products with a high water content, which are very common on the Swiss market (facial care products, moisturizers, lotions, gels, etc.).
In formulations where the aw is sufficiently low, bacterial or fungal growth becomes virtually impossible, even with reduced use of preservatives.
Physicochemical stability
Free water influences reactions:
hydrolysis,
oxidation,
asset impairment,
texture modification (separation, phase shift, hardening).
Precise control of water activity increases product stability, particularly in environments where temperature and humidity vary greatly—conditions that are common in Central Europe and Switzerland (altitude, distinct seasons, storage in pharmacies or institutes).
Clean formulation and reduced preservatives
Switzerland, like many European countries, values natural, minimalist, and clean-label cosmetics.
Knowing the aw allows you to optimize the formula for:
reduce the amount of preservatives,
favor natural stabilization (polyols, humectants, dry structures),
design safer and more sustainable products.
This perfectly meets the requirements of Swiss consumers, who are attentive to quality, sustainability, and transparency.
Water activity reinforces compliance with good manufacturing practices (GMP), which is essential for audits, DIP, and continuous quality control.
Examples of applications
Mountain/sports products : Gels, emulsions, and balms require optimal stability in the face of variations in altitude and temperature.
Natural/organic cosmetics : highly sought after, they often contain few preservatives, which makes AW essential.
Solid growth products : solid shampoos, solid deodorants, cleansing bars — all require an aw measurement to confirm their low microbiological risk.
Premium ranges : The Swiss market prioritizes quality and sustainability, two aspects directly linked to AW.
The aw analysis services offered by Laboratoires Lelegard
We provide manufacturers, brands, distributors, and retailers with:
A precise AW analysis, suitable for all types of cosmetic formulations.
Quality support, in Switzerland and Europe.
Formulation assistance, to stabilize your products or reduce preservatives.
Reports you can use in your DIP, your quality controls, audits, or CPNP/SwissReg files.
Our expertise guarantees reliable, fast results that comply with French, European, and Swiss market requirements.
Water activity (aw) is a technical parameter, but one that is essential for ensuring the safety, stability, and regulatory compliance of cosmetics. For brands targeting the Swiss market, which is known for its high standards and rigor, controlling aw is a real asset in terms of quality and differentiation.
To enhance the quality of your products and ensure the success of your launches in France, Europe, and Switzerland, our AW analysis services provide you with precision, efficiency, and expertise.