What Should We Understand About Shelf Life and Expiration Date?

What is a product's shelf life?

A product’s “shelf life” generally means the length of time you can expect a product to look and act as expected and to stay safe for use. This length of time varies, depending on the type of product, how it is used, and how it is stored. [1]

Shelf-life is predicted from stability studies. Temperature, humidity, lighting, temperature fluctuations, type of container, effects of opening and closing containers and microbial content form the core of stability study design. Many parameters need to be considered when designing a stability study and the reason for the incorporation of some parameters may not be immediately apparent. For example, containers are stored upright and inverted to detect any interactions with the container closure. [2]

What is Expiry or Expiration Date?

The expiry date is the date when a given batch reaches the end of its shelf-life. In determining an expiry date, a range of characteristics of the product are studied over time. The expiry date may be set as a fixed time after manufacture, dispensing or opening of the manufacturer's container. After the expiry date, the product does not necessarily become useless, as it may only have reached the potency limit of the active ingredient. If, however, other physicochemical characteristics (such as pH, dissolution rate of tablets and capsules, particle size in creams and suspensions) have changed, or toxic degradation products reach unacceptable levels, use of the product may be harmful. [3]

Sources:

[1] https://www.fda.gov/Cosmetics/Labeling/ExpirationDating/default.htm (U.S Department of Health and Human Services)

[2] https://www.fsai.ie/faq/shelf_life/best_before_and_use_by.html (The Food Safety Authority of Ireland)

[3] EXPERIMENTAL AND CLINICAL PHARMACOLOGY / Aust Prescr 1994;17:46-81 Apr 1994DOI:10.18773 / austprescr.1994.051