What is Patch test and expiry?
Test a new product on a small area first, and check the PAO jar symbol.
Short answer
Open jars with no preservatives and no clear period-after-opening date.
Patch test and expiry when buying a skin care
Test a new product on a small area first, and check the PAO jar symbol.
Why it matters: Actives oxidise and degrade; a retinol bought two years ago may be useless.
Look for: Open jars with no preservatives and no clear period-after-opening date.
Full Skin Care buying guide