I’m reblogging this post so you can tell where the extract below is from. If you are interested in reading the rest of it. I have known for a while that to get the best out of your acids and retinol on your skin you need to give your skin time after using acids for absorption and then apply retinol when the skins ph may have regulated back. In timenpast, retinol didnt work for me and here is why .

As I mentioned above, the pH concern isn’t about allowing retinol to function, but allowing the skin to optimally convert it to tretinoin. When a correctly formulated hydroxy acid or L-ascorbic acid (vitamin C) product is applied to the skin, the skin is saturated with the product, and the pH (of the skin) is temporarily lowered to something close to that of the product. Glycolic acid, an alpha hydroxy acid, requires an approximate pH of <4.0 to exfoliate and penetrate the skin, while L-ascorbic acid requires a pH of <3.5. Therefore, because the pH necessary for the skin to optimally convert retinol into tretinoin is far more neutral than that, they shouldn’t be used together. Not to mention that, while pH doesn’t affect retinol all that much, it does affect hydroxy acids and vitamin-C. So if used together, the retinol won’t be optimally converted to tretinoin, and the hydroxy acid or vitamin C may not even work much at all! Talk about a “lose-lose” scenario!

Now, it’s important to note (like I said in Part I), that the pH range of 5.0-6.0 was estimated and is only required for the enzymes to convert OPTIMALLY. Since no studies have been done to compare how well the skin converts retinol to tretinoin across various pH values, right now it’s really just a “better-safe-than-sorry” attitude that I make this recommendation.

Also, keep in mind that when I say “used together” I mean like both products (retinol + acidic) are applied one after the other, with no significant wait time in between, or if they’re in the same formulation. I don’t mean that they can’t be used in the same routine. And once again, because no study has been done to see how quickly the skin homeostatically returns to its normal pH when a topical product of a different pH is applied (probably because there are too many factors that are difficult to control and can drastically alter results such as: vehicle occlusion, amount of product applied, and every individuals’ skin pH, etc…), it’s still a “better-safe-than-sorry” approach and recommendation: to apply them on different days. However, if you feel like you MUST use acid products with retinol ones at the same time, wait at least one hour between applications, just to allow for the adequate re-alignment of the skin’s natural pH, and the optimal conversion of retinol to tretinoin.

Why should you wait after using salicylic or glycolic acids before using retinol -specifically ? This answers
Wait 30mins to 1 hour or if you can’t, don’t use an acid toner.