Strength and support together. Calm pairs a low level of retinaldehyde with soothing botanicals, so skin gets vitamin A without the flaking a higher dose brings. Twice a week to start, always over a mist and under an oil, is how most sensitive skin manages it.

Only if you wear makeup or sunscreen. Lift Away dissolves those first and Cleanse then takes care of the skin itself. On a bare-faced day one is plenty. Doubling up every night on dry skin is a reliable way to end up tight and flaky.

That the work is done by plant extracts and oils rather than synthetic actives alone. It does not automatically mean gentler, so the useful question is what is inside: avocado oil and calming botanicals behave very differently from a high-strength acid, whatever their origin.

Six to eight weeks at a gentle pace, with the fourth week usually the turning point. Moving faster tends to buy flaking rather than glow. If skin looks pink the morning after every application, drop back a night and hold there for a fortnight.

Cold air, indoor heating and hot showers all thin the barrier's tolerance, so a serum that suited you in July can sting in January. The answer is usually less frequency and more oil over the top, not a different serum altogether.