Skin barrierStratum corneum · Moisture barrier

The skin's outer defence layer that keeps water in and irritants out.

The skin barrier is the outermost layer of the epidermis, the stratum corneum, and its job is to keep water in and irritants, allergens and microbes out. The usual analogy is a brick wall: flattened dead skin cells as bricks, held in a mortar of ceramides, cholesterol and fatty acids.

It matters because almost every common skin complaint involves it. Dryness, tightness, stinging when products are applied, redness and flaking are usually barrier problems rather than the conditions people diagnose themselves with, and eczema is in large part a barrier disorder.

It is damaged by more things than people expect: over washing, hot water, harsh surfactants, physical scrubs, alcohol heavy toners, too many actives at once, cold dry air and central heating. The modern version is usually self inflicted through an ambitious routine.

Repair is unglamorous and effective. Stop the aggravation, wash less often with a gentle non foaming cleanser and lukewarm water, and moisturise with something containing the lipids the barrier is made of, ceramides, plus a humectant such as glycerine or hyaluronic acid and an occlusive to slow water loss. Most barriers recover within a couple of weeks of being left alone.

Actives should be reintroduced slowly afterwards. Retinoids, exfoliating acids and vitamin C are all reasonable to use and all capable of overwhelming a barrier that is already struggling, particularly when stacked.

Sun protection belongs in the same conversation, since UV damages the barrier as well as the deeper structures, and a compromised barrier is more sensitive to it.

In practice, if your skin stings when you apply things it used to tolerate, the answer is almost always fewer products rather than more, and a fortnight of gentle cleansing and moisturising before adding anything back.

Sources

Related terms