Skin absorption, also known as percutaneous or dermal absorption, is the process by which chemicals or substances pass through the skin and enter the bloodstream or other bodily tissues. This process is crucial in understanding how various substances, from environmental pollutants to topical medications, affect the body.
The Mechanism of Skin Absorption
The skin acts as a barrier, but its effectiveness varies depending on the substance and the individual's skin condition. Several factors influence how readily a substance is absorbed:
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Substance Properties: The chemical's size, solubility (how easily it dissolves in fats or water), and concentration all play a role. For example, fat-soluble substances tend to be absorbed more easily than water-soluble ones. A higher concentration generally means more absorption.
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Skin Condition: The integrity of the skin barrier significantly impacts absorption. Damaged or compromised skin, such as in atopic dermatitis, allows for increased penetration of substances. https://pubmed.ncbi.nlm.nih.gov/27639188/
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Application Method: The method of application affects absorption. For instance, prolonged contact or occlusion (covering the skin) can increase absorption.
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Individual Variations: Age, genetics, and underlying health conditions can influence skin permeability and absorption rates.
Examples of Skin Absorption
Many chemicals used in the workplace, such as pesticides and organic solvents, can be absorbed through the skin and cause organ damage. https://www.cdc.gov/niosh/topics/skin/default.html Topical medications rely on skin absorption to deliver their therapeutic effects. However, not all substances are absorbed easily. For instance, pure vitamin C struggles to penetrate the outer skin layer. https://www.bbc.com/future/article/20240306-what-can-you-absorb-through-your-skin Also, while it's a common misconception, fentanyl generally is not absorbed through the skin from casual exposure. https://health.ucdavis.edu/news/headlines/can-fentanyl-be-absorbed-through-your-skin/2022/10
Studying Skin Absorption
Scientists use various methods, including in vitro tests, to study skin absorption. These tests help evaluate the safety aspects of chemicals and cosmetic formulations. https://www.sciencedirect.com/topics/immunology-and-microbiology/skin-absorption One example is the OECD Guideline 428, which describes an in vitro method for assessing skin absorption. https://www.oecd-ilibrary.org/environment/test-no-428-skin-absorption-in-vitro-method_9789264071087-en
