Airless or not: what packaging does to your skincare

A jar lets fingers in, a dip-tube pump draws air in. What oxidation does to vitamin C and retinol, and why not everything needs to be airless.

Altitude, snow and cold: what actually happens to your skin outdoors

UV rises about ten per cent per 1,000 metres and fresh snow reflects up to eighty per cent of it. Why windburn is really sunburn, and what to do about it.

SPF 30 or 50? The amount matters more than the number

Every SPF number is measured at 2 mg/cm2 and almost nobody applies that much. What the number means, how much you actually need, and which claims Europe bans on the label.

Why vitamin C serums turn brown, and what stops it

An orange serum has stopped working. Ferulic acid is what slows that down. What it does and why you almost never buy it on its own.

Post-workout skincare: your pores do not open (and what does happen)

Pores have no muscles and cannot open or close. What actually happens to your skin during exercise, and the three steps that follow from it.

Aloe vera: when it helps and when it does not

Aloe soothes warm, tight skin and holds water. What it does, when it works against you, and why soothing is not the same as repairing.