Annette Anxiously Asks: I read your post on mineral oil myths. I`m curious about using mineral oil with skin care ingredients that should penetrate the skin (Vitamin C, for example). Does mineral oil prevent their absorption? I would hate to spend a fortune on Vitamin C serums to then find the cheap mineral oil I was using was preventing them working. The Left Brain responds:

To be safe, you should apply “active” ingredients like Vitamin C or even sunscreens BEFORE you apply anything else. This is especially true if you’re using straight mineral oil, because it can set up a barrier on top of your skin.

But what about a Vitamin C lotion that contains mineral oil? Will that prevent absorbtion? Probably not. While occlusive ingredients, like mineral oil, can impede penetration of some ingredients, it depends on what else is in the formula to help drive the actives into the skin. This varies from formula to formula. If you’re buying a well-formulated product from a reputable manufacturer, they’ve probably done their home work to test the product to make sure it works as they claim.