Skincare University

TEWL, moisture, sebum—understanding your skin by the numbers

LEVEL 3
What "Suits Your Skin" Means

※ The information in this section is based on Japanese cosmetics regulations (Pharmaceutical and Medical Device Act / 薬機法). Ingredient classifications, permitted concentrations, and labeling requirements may differ in your country or region.
LEVEL 3 What "Suits Your Skin" Means

To scientifically determine whether a product "suits your skin," measuring your skin's condition with numerical data is effective. Here we introduce three important measurement indicators.

Three Measurement Indicators

1. TEWL (Transepidermal Water Loss)
A direct indicator of barrier function status. Healthy forearm values are 5-15 g/m2/h, rising above 20 when the barrier is compromised.

2. Stratum Corneum Moisture (Corneometer value)
Healthy state is 40-60 AU, dropping below 30 in dehydrated conditions.

3. Sebum Level
The optimal range is 100-200 ug/cm2.

Skin Condition Dashboard TEWL (g/m²/h) 5 15 20+ Lower = Healthier Moisture (Corneometer AU) 20 30 60 Higher = Healthier Sebum (µg/cm²) 50 100 200 300+ Optimal Range Matters Healthy Caution Needs Improvement Objectively assess skin condition through numerical data

Sensory Feel and Data Don't Always Align

Products that "feel nice" and products that "improve your numbers" do not necessarily match. Silicone-based serums may feel amazing immediately after application, but TEWL may not improve. Conversely, ceramide-based products may feel unremarkable, yet with continued use, TEWL decreases significantly.

KAIAN develops skincare products based on scientific evidence.
Feel free to ask questions about ingredients and formulations.

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