Every cosmetics season arrives with its own molecule. This autumn it is called NAD plus, and unlike most of its predecessors this one at least has real biology behind it - which is exactly why the story built around it is more interesting than the molecule itself.

NAD plus is a coenzyme the cell uses to produce energy and to repair its own DNA. That is not marketing. That is basic biochemistry, in every textbook. Over the years the amount in the body declines, and with it the ability of cells to work as efficiently as they once did.

The problem is that it does not get into the skin

Here the story gets more complicated than the label wants to admit. The NAD plus molecule is too large and too unstable to pass through skin. So: a product that promised NAD plus in the bottle cannot deliver NAD plus into your cell.

What is actually inside are precursors - smaller molecules the skin can absorb and then convert into NAD plus itself. Most often that is niacinamide, also known as vitamin B3, an ingredient that has been in cosmetics for decades and costs far less when sold under its own real name.

The price of the same logic

Among the products mentioned: a NAD plus serum at 64.90 euros, a cream at 64 euros, a peptide cream at 95 euros, and a serum from a large French house at 195 euros. Four products, roughly the same chemical logic, a spread of a hundred and thirty euros.

A dermatologist who works with one of the brands says the modern in-clinic approach focuses on improving the overall functioning of the skin, so it looks more balanced, brighter and healthier. That is accurate and it is sensible. It is also a sentence that could sit on any bottle from the last thirty years.

The recommendation is to start at 35, when the skin takes its first steps towards maturity. Whether that is a biological threshold or a marketing one is something nobody will answer directly, because the answer is not the same for every person, and because the second answer does not get printed on a box.

What remains useful: niacinamide works, that is established. The question is whether you are paying for it, or for the word printed above it on the label.