Skin permeability is not uniform across the entire body; it varies significantly depending on the location. While skin generally acts as a barrier, protecting us from environmental threats, certain areas are more permeable than others.
Variable Permeability Across the Body
The skin's permeability is determined by the structure of the stratum corneum (SC), the outermost layer of the epidermis. This layer acts as the primary barrier. However, the thickness and composition of the SC differ across body sites. For example, the scrotum and earlobe exhibit higher permeability compared to other areas. Even within a single area like the face, permeability can vary. ScienceDirect Topics: Skin Permeability highlights this variability, emphasizing that the face, a common site for cosmetic application, shows internal permeability differences.
Examples of Variable Permeability:
- High Permeability Sites: Scrotum, earlobe.
- Low Permeability Sites: Most of the body surface, like the back or arms.
- Variable Permeability Sites: The face shows variations in permeability even within its surface area.
Factors Affecting Permeability
Several factors influence skin permeability including:
- Body Location: As previously mentioned, permeability varies significantly across different body sites.
- Age: Skin permeability decreases with age. Infants have significantly more permeable skin than adults. Skin Physiology of the Neonate and Infant details this age-related change.
- Chemical Composition: The permeability of the skin to specific substances depends on their chemical properties. For example, some organic compounds, like DMSO, are readily absorbed through the skin. Chemistry Stack Exchange: Skin Permeability mentions DMSO as an example.
- Skin Condition: The health and integrity of the skin play a crucial role. Damaged or compromised skin is more permeable.
Conclusion
In summary, skin is permeable, but the degree of permeability varies greatly depending on the location and other factors. It's not simply a "yes" or "no" answer.
