Hydration test

The hydration test is an in vivo assessment to measure the hydrating effectiveness of a cosmetic product applied to the skin. Performed using a corneometer , this test quantifies the increase in the water level in the stratum corneum after application of a cream, lotion, mask or serum.

The purpose of this test is to determine a product's ability to improve skin hydration , both short- and long-term. It provides scientific evidence to support marketing claims such as "hydrating," "nourishing," or "plumping."

The hydration test also allows you to:

• Compare the effectiveness of several formulations , before marketing.
• Validate cosmetic performance within the framework of regulatory dossiers (EC Regulation No. 1223/2009).
• Evaluate skin tolerance and the immediate or lasting effect of a treatment on the skin.

Analytical methods and equipment used

The corneometer is the reference instrument for measuring skin hydration. It works on a capacitive , measuring the variation of the skin's dielectric constant as a function of its water content.

The test protocol generally follows the following steps:

1. Application of the test product and the control (untreated) on a defined area (forearm, cheek, back of the hand).
2. hydration measurement
3. Successive measurements after 30 minutes, 2 hours, 4 hours, 8 hours, or even several days to assess the persistence of the effect.
4. Statistical analysis of the results to determine the significant increase in hydration rate compared to the control.

Other instruments can complement the assessment:

• Evaporimeter for measuring transepidermal water loss (TEWL).
• Cutometer to assess skin elasticity.
• Colorimeter or macroscopic camera to observe skin texture and radiance.

Products and matrices concerned

This test is applicable to all cosmetic products intended for moisturizing , in particular:

• Face and body creams , anti-aging or nourishing treatments.
• lotions, gels and serums .
• Repairing masks, milks and balms
• Sun and after-sun products , whose moisturizing effectiveness is a key argument.
• Gentle dermatological products for dry, sensitive or dehydrated skin.

Tests may be carried out on healthy volunteers under dermatological supervision, in compliance with good clinical practices.

Industrial and regulatory applications

The hydration test is part of the cosmetic efficacy studies required for:

• Validate marketing claims (“hydrates the skin for 8 hours”, “immediate effect”…).
• Compile the proof of efficacy file required by the European Cosmetic Regulation.
• Optimize formulations during the development phase.
• Ensure consumer satisfaction and product compliance before marketing.

This test is often combined with other complementary studies for a complete evaluation of the performance of the treatment.

Related analyses

YesWeLab recommends combining the hydration test with other cosmetic tests for a complete evaluation:

• Skin sensitivity test to check product tolerance.
• Study of the photostability of a sunscreen product for formulas containing UV filters.
• Accelerated stability test to assess the durability of moisturizing products.
• Stability and compatibility tests to verify the interaction between the container and the contents.
• Elastin or collagen to correlate hydration and skin tone.

YesWeLab expertise

YesWeLab collaborates with a network of ISO 17025 and COFRAC accredited laboratories , specialized in cosmetic testing and in vivo clinical trials .

Thanks to the YesWeLab digital platform , you can centralize your analysis requests , track your tests online and receive your certified reports with ease.