In cosmetic products, stability is the ability to maintain their specifications within the limits set by the manufacturer or formulator during the shelf life and during the use of the product. The latter is determined by the In-Use Stability Study.

When a container is opened and closed repeatedly over time and the product is handled by the user, the exposure of the article to oxygen, moisture and microorganisms increases, which can cause significant variations during the period of time in which the product is used.

At Dr. Goya Análisis we evaluate the stability of the product during its use, simulating the manipulation to which it will be subjected during the expected time of use and under the recommended conditions, measuring the parameters susceptible to change with a frequency that will vary depending on the type of product. In this way, it is evaluated whether it remains in accordance with its specifications during the period in which it is open.

The test is normally carried out in two batches, preferably industrial, one of the batches being close to the end of the shelf life of the product, in a container that maintains all the specifications of the container to be marketed, i.e. same material, volume and dispensing.

In-Use Stability is especially recommended for those products for which the risk of degradation is higher after opening the container. Examples of these products include sterile preparations, products that are reconstituted as a suspension or solution, oxidisable products or non-sterile products with an intended use of more than 1 month with wide-mouth packaging, among others.

It is important to note that this study is an integral part of the stability assessment of a product, as it allows manufacturers to ensure that products maintain their quality during the intended time of use.

Laura Rubio
Head of Stability Department at Dr. Goya Análisis