Skin barrier

The skin barrier is the outermost layer of the epidermis — dead cells held together by lipids, usually described as bricks and mortar. Its job is to keep water in and irritants out.

When it is working you do not notice it. When it is damaged you get a specific set of symptoms: tightness after washing, stinging from products you used to tolerate, redness that will not settle, flaking, and skin that suddenly reacts to the weather.

What damages it: over-washing, hot water, alcohol-heavy toners, scrubs, using acids too often, starting a retinoid too fast, and — most commonly — several of those at once.

What repairs it: doing less. A gentle cleanser, a ceramide moisturiser, sunscreen, and no actives for four to six weeks. Centella and panthenol help. Most barriers recover fully in that time, which is why 'sensitive skin' is often temporary rather than a skin type.

The mistake to avoid is treating the symptoms as a new problem and adding more products. The barrier is damaged by the routine; it is repaired by a shorter one.