How Deep Does Skincare Penetrate The Skin?

How Deep Does Skincare Penetrate The Skin?

Sabrina Schrope

Cosmetic Chemist, Owner of Vitamin You

 

Introduction:

             One of my favorite duties of running a small skincare shop is talking to customers and hearing how they interact with skincare and the beauty industry. Unfortunately, there’s a lot of misinformation on the internet but I’m glad that I can help inform people about what’s scientifically correct or not. One of those beliefs being rubbing essential oil in the belly button to achieve a detox or therapeutic affect- which is not true, and this article will explain why.

 

Skin Biology:

             The skin has three major functions: temperature regulation, metabolic processes, and protection. Beginning from the outermost layer to the inner most, skin cells work to prevent bacterial growth, protect from UV exposure, and prevent infections. Any and all actives or foreign bodies must travel through the skin’s obstacle course to even reach the lower layers of skin, where they then would be subjected to the body’s macrophages and Langerhans cells as part of the immune system.

 

Below is an image depicting the various layers of the skin that was created by Nursing Times1. The citation is at the end, please give it a read for a more in-depth understanding of the skin and its functions!

            It’s understood that roughly 500 Daltons (g/mol) is the largest size a chemical can be to even penetrate the outermost layer of skin. Due to this extremely small size requirement and how affective the skin barrier is at protecting the lower layers, it’s a difficult job for a cosmetic chemist to be able to affectively deliver actives to lower layers. Larger compounds might have a chance if they’re transferred in a medium that’s both water and oil loving (amphiphilic). These are creams, lotions, and moisturizers that use emulsifiers and why our Hyaluronic Acid Serum is not a water-only gel, but instead a milky gel to aid in hydration and penetration.

 

            There are certain compounds that are able to successfully reach the bottom layers, heavy metals for example, which are restricted or illegal to have in cosmetics. Consumer safety is handled by The Food and Drug Administration (FDA) in the USA which hold all cosmetics to the same standard: Must be safe for consumer use when used as directed. Pharmaceutical creams and treatments are highly regulated because of their penetration too.

 

It’s estimated that only 10% of any product can even reach the stratum granulosum. Please refer to the image again, this is still a layer within the epidermis, where there are no blood vessels. This 10% may be oil soluble actives, humectants, carbon dioxide, and therapeutic compounds like steroids.

 

Conclusion

            The skin’s main function is to protect the body from external objects and microbes. My formulation instructor always used the metaphor of a needle (skin active ingredient) having to cross an entire football field (the epidermis) to be able to reach the area filled with collagen and elastin. Applying safe and legal over-the-counter skincare products externally will not reach the blood stream. Only oil soluble actives, humectants, and therapeutic compounds are able to reach the stratum granulosum when put into an amphiphilic formula. Anything beyond this will be attacked by white blood cells. This is why applying essential oil to the belly button will not do anything besides cause irritation and greasiness.

 

Citation

1 (2019). “Skin 1: the structure and functions of the skin”. Nursing Times. Fig 2. Layers of the skin. Accessed Sep. 13th 2023. < https://www.nursingtimes.net/clinical-archive/dermatology/skin-1-the-structure-and-functions-of-the-skin-25-11-2019/>.

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