73% skincare. What does that actually mean?

A percentage can make a beauty promise feel wonderfully precise. It looks like an answer before we have even worked out the question. But when makeup announces how much of it is skincare, what are we actually being told?

MAC’s Studio Radiance Skin Tint Stick is an especially interesting example. The UK product page describes a formula containing 73% skincare ingredients and promises hydration and wear lasting 24 hours. It names radish seed and açaí extracts among its ingredients. Those are the brand’s claims, rather than findings from a wear test by this magazine. [1]

The first question is pleasantly unglamorous: how was that number calculated? Which ingredients were counted, and on what basis? The page reviewed does not explain the calculation. Its ingredient list names emollient-type materials alongside waxes, powders and botanical extracts, but does not give their individual percentages. We cannot reconstruct the advertised figure from that list. [1]

More fundamentally, a formula percentage and a performance result answer different questions. Even if the arithmetic is entirely sound, it cannot by itself tell a shopper how much more hydrated their skin will become, how long a benefit will persist or whether this stick performs better than another foundation.

There is nothing inherently absurd about makeup offering a skin benefit. Nor does a familiar moisturising ingredient need a glamorous origin story to be useful. The difficulty arrives when the reputation of an ingredient starts doing the work of evidence about the finished product.

The 2017 technical guidance on cosmetic claims makes that distinction explicit: an ingredient’s properties should not be presented as properties of the finished formula unless that implication is justified. This is non-binding best-practice guidance, not a verdict on MAC or a legal finding by this magazine. It is nevertheless a useful editorial test: ask what was demonstrated in the product someone will actually buy. [2]

Hydration can be measured. Published research has used instruments such as a Corneometer to assess the outer skin’s water-related electrical properties, comparing readings at different times and after different formulations. That research explains a measurement approach; it does not test this MAC stick. [3]

For a meaningful appraisal of this particular claim, we would want the test method, number of participants, application amount, comparison condition, measurement times and size of the observed change. We would also want to know whether the test conditions resemble how people use the product.

A detectable change in an instrument reading is not automatically a dramatic improvement someone will notice in the mirror. And a claim about colour remaining on the face is different from a claim about hydration: one result cannot stand in for the other.

The public product page reviewed supplies claims and an ingredient list, but not the study report or those methodological details. We have not obtained MAC’s underlying evidence or conducted our own controlled test. We therefore cannot grade the strength of that unpublished evidence, confirm the promised duration independently, or declare that the claim is merely fluff. [1]

That distinction matters. “We cannot verify it from the information available here” is a defensible conclusion. “It does nothing” would be a leap.

If you like the idea of a portable, sheer base, judge its shade and finish as makeup. For the skincare promise, ask for the evidence behind the duration and the meaning of the percentage. A convincing answer should leave you understanding more, rather than simply admiring the number.

A beautiful finish can be a perfectly good reason to enjoy makeup. It should not have to masquerade as a scientific breakthrough. Equally, a genuine skin benefit deserves evidence clear enough for a curious reader to inspect. That is the standard we will keep asking for.