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The “moisturizing” claim is one of the most widely used in cosmetics, especially for face creams, body lotions, serums, and masks. However, to back this claim, Responsible Persons must provide concrete evidence of the product’s effectiveness in enhancing skin hydration. This article delves into approaches for substantiating moisturizing claims, regulatory requirements, and the methods for measuring the moisturizing efficacy of cosmetic products.

The importance of a sustainable claim

A cosmetic claim, which describes a product’s properties or benefits, must be truthful, clear, and scientifically supported. Regulatory bodies, like the European Commission, require that each claim is backed by evidence proving its validity to prevent misleading practices. The “moisturizing” claim is no exception; it must be substantiated by rigorous studies to ensure accuracy and consumer trust.

Regulatory requirements for the moisturizing claim

The European legislation on cosmetic products (EC Regulation No. 1223/2009) establishes that each cosmetic claim must be verified through adequate and demonstrable data. To ensure compliance, the “moisturizing” claim must also comply with the “Claims Regulation” (EC Regulation No. 655/2013), which introduces common principles for assessing the veracity of claims. The main requirements for a cosmetic claim include, among others:

1. Truthfulness: The product must actually provide a moisturizing benefit.
2. Scientific support: Evidence must be obtained through recognized tests and methods.
3. Honesty: The claim must not mislead the consumer about the characteristics of the product.
4. Evidence: Companies must maintain adequate documentation confirming the declared effectiveness.

Regulatory authorities may require companies to provide such evidence in the event of verification, and it is therefore crucial that the claim is supported by solid data.

Methods for substantiating the moisturizing claim

To prove that a cosmetic product has moisturizing properties, clinical, instrumental or sensory studies must be conducted. These methods vary in complexity, cost, and accuracy, but are critical to providing a solid foundation for supporting the claim.

1. In vivo clinical studies

In vivo clinical studies offer the most direct approach to assessing a cosmetic product’s moisturizing effectiveness on human skin. These studies typically involve applying the product to a group of volunteers over a specified period, with results gathered through both objective and, at times, subjective measurements.

One of the most widely used methods in clinical studies for skin hydration is the use of the Corneometer, a device that measures the water content in the stratum corneum, the outermost part of the skin. The Corneometer works by exploiting the electrical properties of water: the higher the water content, the greater the dielectric capacity of the skin, measured by the instrument.

Another instrumental method used is the Tewameter, which measures transepidermal water loss (TEWL)—the amount of water evaporating from the skin’s surface. An effective moisturizer should reduce this loss.

2. Test in vitro

In addition to vivo clinical trials, laboratory techniques can simulate human skin conditions. These in vitro tests help identify a product’s moisturizing potential based on individual ingredients before human application.

One widely used method is reconstituted skin models—synthetic tissues that replicate human skin structure, enabling hydration tests without involving volunteers. These models test a product or ingredient’s capacity to retain water and enhance the skin barrier.

3. Sensory Studies

The subjective experience of consumers is also important to substantiate the moisturizing claim. Sensory studies are based on subjective assessments provided by participants regarding the perception of hydration after use of the product. While these studies do not offer quantitative measures, they are useful for understanding how consumers perceive the effectiveness of the product.

Consumers can complete questionnaires on skin softness, comfort, and dryness reduction. These results complement instrumental data, providing a fuller picture of the product’s effectiveness.

Moisturizing ingredients: evidence of efficacy

The moisturizing effectiveness of a product depends to a large extent on the ingredients contained in its formula. Some ingredients, such as hyaluronic acid, glycerine, panthenol, and aloe vera, are known for their moisturizing properties. However, even then, it is important to demonstrate that these ingredients are present in effective concentrations and that they work in the context of the final formulation.

Hyaluronic acid, for example, is known for its ability to retain water, improving skin hydration. Scientific studies have shown that topical use of hyaluronic acid can increase skin hydration and improve skin elasticity. Similarly, glycerin is a humectant that draws water from its surroundings and the skin itself, helping to keep the skin hydrated.

Conclusion

Substantiating the moisturizing claim of a cosmetic requires a multidisciplinary approach, combining in vivo, in vitro and sensory scientific studies. Regulations require cosmetic companies to rigorously and verifiably demonstrate the moisturizing efficacy of their products, through recognized tests and documented evidence. The use of tools such as the Corneometer and the Tewameter, combined with proven ingredients, makes it possible to guarantee the veracity of the claim and to provide the consumer with quality products.

Taobé Consulting supports clients in complying with EU Cosmetics Regulation 1223/2009 by ensuring cosmetic claims align with regulatory standards on substantiation, scientific evidence, and fairness. We provide guidance on crafting responsible and transparent claims, focusing on the common criteria: legal compliance, clarity, honesty, fairness, informed choice, and product efficacy. Our expertise helps brands substantiate claims with robust data, manage evolving regulatory demands, and uphold consumer trust. This ensures products meet regulatory expectations, while maintaining brand integrity and consumer confidence.