LEVEL 5
Skin Structure & Science
Skin is not merely a "covering." It houses resident immune cells, is richly innervated, and responds to hormones -- skin is the body's largest immune and neural organ, sometimes called the "second brain."
The epidermis hosts resident Langerhans cells -- immune cells that capture foreign invaders (antigens) and perform antigen presentation to T cells in lymph nodes, signaling "there's an enemy here." UV radiation is known to reduce and impair these Langerhans cells.
Skin keratinocytes produce antimicrobial peptides that fight bacteria and viruses. The key players are beta-defensins and cathelicidin (LL-37). In atopic dermatitis patients, production of these peptides is reduced, increasing susceptibility to Staphylococcus aureus infection.
TRPV1 is a receptor that responds to capsaicin (the spicy compound in chili peppers) and heat, expressed on skin sensory nerves. When activated, it releases neuropeptides like Substance P, causing vasodilation, inflammation, and itching. It's gaining attention as a factor in sensitive skin and rosacea.
Psychological stress triggers the hypothalamus to release CRH (Corticotropin-Releasing Hormone), ultimately raising cortisol levels. Cortisol impairs the stratum corneum barrier, increases TEWL, and promotes inflammation. "Stress causes skin problems" is scientific fact.
The emerging concept of the Gut-Brain-Skin Axis describes how the brain, gut, and skin are intimately connected through immune signaling and neural communication. Gut microbiome disruption affects atopic dermatitis and acne, and conversely, skin inflammation can alter intestinal permeability. Here lies the scientific basis for why diet, sleep, and stress management directly impact skin health -- not just skincare products alone.
KAIAN develops skincare products based on scientific evidence.
Feel free to ask questions about ingredients and formulations.
