Skin Penetration Basics

Skin Penetration

• Skin penetration refers to the process by which substances, such as topical medications, chemicals, or pathogens, enter the skin.
• The skin's primary function is to act as a barrier, preventing the entry of harmful substances and microorganisms.
• Penetration varies based on the substance's chemical properties, the skin's condition, and the application method.
• Factors influencing penetration include the substance's molecular weight, lipophilicity, and solubility.
• Skin layers play a critical role in penetration; the stratum corneum, the outermost layer, is the primary barrier.
• The stratum corneum is composed of corneocytes, lipids, and intercellular spaces.
• Penetration is influenced by the integrity of the stratum corneum; damage or disruption increases penetration potential.
• Certain topical medications are designed to target specific skin layers for optimal effectiveness. Skin penetration also varies across different skin types and locations on the body.
• Factors like age and health conditions affect skin barrier function, contributing to variations in penetration rates.
• Transdermal drug delivery systems capitalize on skin penetration to deliver medications through the skin.

Skin Function

• The skin's core function is protection, acting as a barrier against environmental stressors.
• It protects against pathogens, UV radiation, and physical trauma.
• Regulation of body temperature, via sweating and blood vessel dilation, is a critical function.
• The skin aids in sensation, providing feedback through touch receptors.
• Vitamin D synthesis in response to UV radiation is a crucial biological process.
• Cutaneous immune response plays a crucial role in protecting the body from pathogens.
• The skin houses several types of cells that support its various functions.
• Maintaining hydration and electrolyte balance is aided by skin barrier function.
• The skin contains sensory receptors for touch, temperature, pressure, and pain.
• Wound healing, tissue repair, and regeneration depend on skin functions.

Mechanisms of Skin Penetration

• Passive diffusion is a primary mechanism for many substances crossing the stratum corneum.
• The process involves the movement of substances from higher concentration areas to lower concentration areas along a concentration gradient.
• Substances that are lipid-soluble tend to permeate the stratum corneum more readily.
• Substances with a high water solubility may move through via transepidermal water loss channels.
• Substances may be transported via an active mechanism, requiring cellular energy.
• Ion channels and carrier-mediated processes can facilitate active transport.