What is TEWL, and why is it important?

TEWL is the abbreviation for the English term "transepidermal water loss": water lost through evaporation from the skin. Every skin loses some water, and this is natural. The important thing is that this loss remains balanced.

The measurable indicator of the barrier

In dermatology research, TEWL is one of the most frequently used indicators of barrier function. When the barrier is intact, water loss is low and balanced. When the lipid mortar between the cells weakens, water evaporates more easily and the TEWL value increases.

The skin also makes you feel this without the need for a measuring device. Long-lasting tightness after washing your face, a flaky appearance, cream disappearing quickly, or products that previously caused no problems starting to sting can be clues that water loss has increased.

Habits that increase TEWL

• Frequent washing with hot water and harsh, heavily foaming cleansers
• Using multiple strong actives on top of each other in the same routine
• Dry indoor air, wind, and cold
• Unprotected sun exposure

The approach that supports the barrier

The way to balance water loss is to support the barrier's own structure. This has three legs:

• Complete: Skin-like lipids such as Ceramide NP help fill the gaps in the mortar.
• Hold: Humectants such as hyaluronic acid help retain water in the upper layers of the skin.
• Cover: Plant oils help slow down evaporation by forming a thin layer on the surface.

Niacinamide also holds an important place in this table because it supports the skin's own ceramide synthesis.

In short

TEWL is the way your skin tells you what condition the barrier is in. Reading the tightness as a warning and simplifying your care gives your skin time to return to its own balance.