I have been asked this question about skincare products a zillion times in my career and the answer is always the same it all depends on the particular item! I know, I know, that is a very evasive answer so I will clarify. The answer is obvious on any product with an expiration date, of course. Anything that is a Pharmaceutical Prescription such as Obagi Tretinon or Hydroquinone in products such as Clear/Blender and C+Hydroquinone in the wildly popular (and my own personal favorite) C-RX System have clear dates on the package. If you are using these products properly, they will run out ages prior to the expiration date.
Topical Vitimain C, L-Ascorbic Acid is the skincare product most patients question as it has a tendency to oxidize, just as an apple will oxidize once it is cut. The normally honey colored serum turns more amber as it is exposed to air and light, although it is still efficacious. This has been proven and studied for years by Dr. Sheldon Pinell, Head of Dermatology at Duke University and the founder of SkinCeuticals L-Ascorbic Acid. So, with a pedigree that fabulous, I tend to listen!
In general, most skincare products will last about 2 years if unopened and if stored in a cool, dry place, not your powder room. Store products in a dresser draw if possible to avoid any change in tempeture and unnecessary exposure to light. Once opened, most products are still viable for about 12-18 months due to exposure to air and light which contributes to the oxiditition process where the ingredients slowly begin to destabilize and become less efficacious. On most skincare packages, you will find an icon that resembles an opened jar with a number followed by the letter (M). This is how many months it stays effective after it has been opened. Also, when you see an adorable white bunny with pink ears, this indicates that a product is cruelty free.
Beauty Wishes to All, Penny!