Kitster’s question…I’m a bit confused about mineral oil. Is it absorbed into the skin at all or does it just sit on top of the skin forming a layer? My favourite moisturiser is mineral oil based and I use physical sunscreen on top of it which contains some good stuff for skin eg antioxidants etc. So does the mineral oil in my moisturiser prevent ingredients in my sunscreen from reaching my skin?
The Beauty Brains respond:
First of all, let’s clarify that mineral oil (M.O.) only penetrates into the upper layers of the stratum corneum. It is not absorbed through the skin into the dermis. It does form a film although that film is not necessarily entirely contiguous – in other words there will be gaps in the film. In moisturizing lotions, this film does a good job of keeping water from getting OUT of the skin because it is so hydrophobic. But, to paraphrase your question, does the film keep other ingredients from getting TO the skin?
Mineral oil is used in sunscreens
Based solely on the fact that mineral oil is used in sunscreens, I have to say the answer is no. That’s because when M.O. containing sunscreens are tested they are shown to provide UV protection which indicates that the sunscreen active is getting to the upper layers of of skin. This diffusion takes a little while which is why you should put sunscreen on 30 minutes before going into the sun.
Mineral oil does not stop drug penetration
If that’s not proof enough, I found a study which evaluated the effect of varying the water and mineral oil ratio on the diffusion rate of sulphathiazole from cold cream type ointments. In this study they took creams that contained from 8% to 83% mineral oil and measured how well a specific drug ingredient diffused out of the cream. The study was done in the lab, not on skin, but the results showed that even at the highest level of M.O the drug still diffused through the cream. Granted though, it diffused much faster at lower levels. Mineral oil is rarely used at very high levels in creams so this indicates there’s not really any problem.
The Beauty Brains bottom line
Considering that sunscreens are demonstrated to be efficacious even when they contain mineral oil (and considering that at least some active ingredients have been shown to diffuse through mineral oil) it doesn’t seem like there’s much to be worried about.
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This is good to know! Thanks for explaining, and sharing your insight.
Thanks for sharing this awesome information…
I usually have very dry skin in the winter months. It gets so bad that the backs of my hands crack and bleed. This year I am rubbing mineral (baby) oil on my skin after showering every morning. I wipe off the exces with a towel so that my skin is not oily. It has worked wonders! My hands are supple and the rest of my skin doesn’t itch. I did run out of time one morning and omit the oil – my skin itched all over!
Is there a difference when mineral oil is in an emulsion, or at least partially emulsified in the 83%? In the case of an emulsion the water soluble components would migrate via diffusion (etc.) through the water (aqueous phase) within the lotion. Would 100% mineral oil create a barrier?
Damn, we have a smart audience! I can’t find any data on this but my educated guess is that it won’t make a difference because the water phase evaporates leaving behind the oil phase anyway.
I was wondering if this is also true for silicones (or dimethicone to be more specific) in skin care or hair care products ?
I think if you’re trying to apply another ingredient on top of a film of dimethicone (especially if that ingredient is water soluble) then it could be a problem. We used to do a demonstration with a hair tress which had been treated with a dimethicone conditioner. After the hair tress dries (so the silicone has a chance to set up a film) you can put a drop of water on the hair and it will just roll off because the dimethicone is such a good barrier.
But if you’re applying a product that has dimethicone and other ingredients together in an emulsion, the other ingredients have a chance to reach the hair or skin before the barrier film “sets up.”
Thank you for this information! So applying coconut oil as a leave-in conditioner, after using a shampoo that contains a fair amount of dimenthicone, is probably not very effective?
Anything that can impede the penetration of the coconut oil could theoretically reduce its efficacy. For best results you should use a non-conditioning shampoo before applying coconut oil.
Thank you ever so much for this info 🙂 It’s really helpful!
We’re here to help, Kitster!
I make up a body moisturiser using roughly 1/3 each of mineral oil, glycerin and water. I’ve added coconut oil before, but wasn’t sure if it would diffuse through the mineral oil to the skin and add any extra benefit. Glad to know it may well be doing its thing after all. So why do aromatherapy texts always say the carrier oil must be vegetable? Thanks for all the great info and the work you do.
Hello Beauty brains!
I used your website many times and usually find my answers quite easily, thank you for all the precious information you’re providing us.
This time, I’m wondering wether or not vegetable (not mineral) oils are harmful in the context of sun exposure and can’t find an answer. It seems obvious to me that they wont protect you from UV, but do they increase UV absorption (alone or emulsified)?
Why would sunscreen actives have to reach the upper layers of skin to be effective? Just like a hat, couldn’t the actives just sit on top/in the mineral oil above the skin and block/absorb the U.V. just fine?
Think of it this way: Instead of one big hat you’re using thousands of tiny hats. When you first put them on your head they’re not sitting in the right place – they’re stacked on top of one another and they’re all crooked. Given a little time, as you shake your head around, the hats slide down and cover your head in an even layer.
It’s an odd analogy but that’s kind of how it works.