LEVEL 5
Skin Concern Care Guide
"I have sensitive skin" — many people identify themselves this way. However, from a dermatological science perspective, sensitive skin is not an innate "skin type" but rather a "condition" where barrier function has broken down. This means it can potentially be improved with appropriate care.
The mechanism of sensitive skin can be understood as a vicious cycle. First, when barrier function declines due to some cause (excessive cleansing, dry environment, stress, etc.), TEWL (transepidermal water loss) increases. In skin with weakened barriers, external irritants easily penetrate, triggering an inflammatory cascade (a chain reaction of inflammatory cytokines such as IL-1α, TNF-α, and IL-6). This inflammation further destroys barrier function, completing the vicious cycle.
The key to barrier repair is ceramides. Ceramides account for about 50% of the intercellular lipids in the stratum corneum, but their types and ratios matter. In healthy skin, ceramide NS (non-hydroxy fatty acid sphingosine type) comprises about 50%, ceramide NP (non-hydroxy fatty acid phytosphingosine type) about 25%, and ceramide AP (alpha-hydroxy fatty acid phytosphingosine type) about 25%. Formulations that mimic this ratio are considered most effective at repairing the barrier.
The role of the skin microbiome (commensal flora) has gained increasing attention in recent years. Healthy skin surfaces host beneficial bacteria including S. epidermidis (Staphylococcus epidermidis), which suppress pathogenic bacterial growth and maintain immune homeostasis. In skin with disrupted barriers, this microbial balance collapses (dysbiosis), allowing harmful bacteria such as S. aureus (Staphylococcus aureus) to dominate.
Fermented ingredients (lactobacillus ferment filtrate, yeast ferment extract, etc.) function as prebiotics that serve as nutrients for beneficial bacteria, promoting the recovery of healthy flora. Additionally, organic acids and peptides produced during fermentation maintain skin pH at a mildly acidic level, creating an environment favorable for beneficial bacteria.
The "stinging" and "tingling" sensations felt by sensitive skin are caused by overactivation of TRPV1 (Transient Receptor Potential Vanilloid 1) receptors present in the epidermis. Originally sensors that detect temperatures above 43°C, in skin with compromised barrier function, the threshold drops, causing activation even from low-concentration stimuli. TRPV1 activation triggers the release of neuropeptides such as Substance P and CGRP, inducing vasodilation (redness) and inflammation — this is "neurogenic inflammation."
Sensitive skin care should scientifically address three pillars: barrier repair (ceramides), microbiome recovery (fermented ingredients), and stimulus avoidance. Rather than simply choosing products labeled "for sensitive skin," understand the science of ingredients and formulation to identify what your skin truly needs.
KAIAN develops skincare products based on scientific evidence.
Feel free to ask questions about ingredients and formulations.
