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I have tried Kersatase shampoo- it smelled a little off.
Clinique cream eyeshadow- it was dry and hard to use

This doesnt boil downt to authenticity. It all boils down to how well established, secure and controlled is their warehouse storage conditions? If an online company doesn't show or prove that they have this down pat (especially selling all sorts of different cosmetics ingredients and items, then do not even think twice to buy from them… Not unless you are willing to pay less for less quality!
Just google search warehouse, cosmetics, standards:
"products may require specific storage conditions, such as temperature or humidity control, to prevent spoilage or degradation. Failure to store these products properly could result in damage to the items, rendering them unsafe for use."

I've fairly normal skin type with ocassional breakouts and congestion, but whenever I use sunscreens and exfoliating products from other brands, my skin gets worse. Not with Jan Marini's products. I've used it for a number of years (10 years+) and feel it work everytime I use it. The key is to be diligent! I'm so grateful to have a skincare line I can always rely on.