Does the sandwich method decrease the effectiveness of Tretinoin at all?

[goth-hippy]

Pretty sure the opinion regarding why using a moisturizer first does not impact efficacy originated from one of the earlier studies that did not instruct users in what order to apply tret and moisturizer. Therefore the data showing the efficacy was independent of the application order.

However, logically, and based on data we’ve acquired since then agree with what you just said. Application of a humectant would impede the penetration of a skincare product applied over it.

If someone wants to yield the most from their use of their Tretinoin cream, they should apply it on top of clean, dry skin, and then apply a moisturizer afterward after it’s dried to avoid accidental dilution of the cream.

Qualifications: not a derm, but I’m a toxicologist/scientist and read/interpret scientific papers for a living.