Shelf life and stability of cosmetic products
Guest contribution by Mag. Dr. Doris Plank
The shelf life of cosmetic products depends on several factors. The shortest minimum shelf life of a raw material is not in every case to be equated with the minimum shelf life of the product, although the initial quality (freshness, stability, etc.) of the raw materials is an essential factor for the shelf life and quality of cosmetic products. The manufacturing process and the packaging also influence the shelf life/stability of the product. Basically, a distinction is made between physico-chemical stability and microbiological stability. What exactly this means is explained in more detail below.
Physico-chemical stability: This can, under certain circumstances, also be determined yourself by means of a natural stability protocol. Here, observations are made using a stability protocol under defined storage conditions to see if changes occur. What is checked here are the sensory properties (appearance, smell, consistency), if possible the pH value, where applicable the microbiological stability, and for oil-based products, the acid value & peroxide value. Naturally, further parameters are also possible depending on the product type. The disadvantage of this method is the long duration of data collection and that you receive no information about the shelf life under stress conditions. What are these stress conditions now? The most common are:
- Exposure to light
- Influence of humidity (keyword: bathroom)
- Freeze-thaw tests
- Influence of high temperatures
Those who do not have the time to determine the physico-chemical stability themselves have the option of carrying out an accelerated stability test. Here, one obtains the necessary information in a short time to assess whether a cosmetic product has a shelf life of more than 30 months. Usually, the following influencing conditions are adjusted: temperature, humidity, mechanical stress & exposure to light. However, the evaluation of the results must be done carefully here. It may be that the special conditions lead to changes that are not to be expected under normal storage.
As a general rule, experience from other products in the same product group and packaging type can provide valuable information when determining shelf life.
Microbiological stability
The water content of the product has a significant influence on microbiological stability: a high water content ensures that bacteria and germs can multiply easily. For this reason, water-containing products (shower gel, creams, cleansing gels, ...) must generally be preserved. The effectiveness of the preservative must be proven by means of a so-called challenge test. In contrast, low-water products (shampoo bars, surfactant bars, balms, oils, soaps, etc.) are more stable even without preservatives.
Packaging: Dispensers, pump sprays, pipettes (when used correctly) – here, contact with the cosmetic is very low. Whereas cream jars, for example, make the product more susceptible to contamination due to their large opening.
Type of application: Deodorant, toothpaste, lip care: These products are usually applied directly from the packaging to the skin or to aids (toothbrush); here, too, the risk of contamination is increased.
In short, the shelf life of cosmetic products depends on many factors. As a manufacturer, you are responsible for the shelf life within the period of use.
How is the shelf life indicated:
For a shelf life of less than 30 months (2.5 years), a minimum shelf life date must be affixed to the label. This must be indicated with the wording "Best before" month/year or day, month and year, or the "egg timer symbol" and indication of the date in month/year or day, month and year.
For a shelf life longer than 30 months, the above paragraph does not apply. The well-known "open cream jar" symbol and the indication of, e.g., 12 months means that the product can still be used for 12 months after it is first opened.
Mag. Dr. Doris Plank | + 43 650 311 38 33 | www.cosmetic-consulting.at | doris@cosmetic-consulting.at
As a chemist with a doctorate and experience in quality management, Doris deals intensively with the composition and (toxicological) effects of modern natural cosmetics and creates, among other things, product information files (PIF) including safety reports for cosmetic products for her clients in accordance with the EU Cosmetics Regulation (EC) No. 1223/2009 as well as its supplementary provisions.
Sources:
https://www.ages.at/mensch/kosmetik/kosmetik-infos-empfehlungen#c6715
GÖCH Working Group "Microbiology" Guide for the practical determination of the Period after Opening (PAO) for cosmetic products
GÖCH Working Group "Cosmetics" Usual PAO indications by product group
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