What is the skin barrier, and why does it wear down?

The brick wall analogy

The top layer of your skin is called the stratum corneum. It's just a few cells thick, thinner than a sheet of paper. Scientists compare it to a brick wall: the neatly stacked cells are the bricks, and the ceramides, cholesterol and fatty acids filling the gaps are the mortar.

When the mortar is intact, it does two jobs. It slows down the water in the lower layers from evaporating away, and it makes it harder for irritants outside to get in.

What wears the barrier down?

Harsh cleansers. Strong foaming surfactants remove dirt, but they also strip away the lipids in the mortar. That tight feeling after washing is the part you can feel.

Hot water. Research shows hot water roughly doubles your skin's water loss and increases redness too. After a shower, skin moisture drops back to its starting level within ten minutes.

Shaving, sun, wind and air conditioning also tire out the top layer. In lab measurements, even a single pass of a razor causes a small disruption in the barrier.

How can you tell it's worn down?

Tightness after washing, flaky dryness, redness that comes on easily, or a product you've always used without trouble suddenly stinging. Fine lines also look more visible on dry skin.

How can you support the barrier?

• 1Wash your face with a gentle, sulfate-free cleanser.
• 2Shower with lukewarm water. Don't rub with the towel, pat dry.
• 3Apply moisturizer while your skin is still slightly damp.
• 4Keep it up every day. In clinical studies, regular moisturizing reduces the look of fine lines.

Prebiotic formulas fit into the cleansing and moisturizing steps of this routine. The aim is to help the barrier do its own job.