Readers Asked, We Answered
The questions that arrive most often at the desk, answered as briefly as accuracy allows.
Is a higher percentage of an active always better?
No. Many actives plateau: niacinamide is well supported at 2–5%, and ascorbic acid effects level off around 20% in the research associated with Sheldon Pinnell. Beyond those points, extra percentage tends to add irritation, not results.
Can I tell the exact percentage from an ingredient list?
No. Ingredients above 1% are listed in descending order, so you can estimate a ceiling — an ingredient cannot exceed the one before it — but not an exact figure. See Reading the Back of the Jar.
Can I use vitamin C and niacinamide together?
Yes. The warning relied on heat and long contact times that do not apply when you layer two serums. Details in What Plays Well Together.
Is retinol the same as tretinoin?
No. Tretinoin is prescription retinoic acid and acts directly on skin receptors. Retinol must be converted in the skin first and is milder at the same percentage.
Why did my vitamin C serum turn orange?
Ascorbic acid oxidises with air, light and heat. A faint straw colour is common; a clearly darker serum has lost potency. Store it cool, closed and away from light.
Does “clean beauty” mean safer?
“Clean” has no legal definition. In the EU and UK every cosmetic needs a safety assessment by a qualified person before sale, regardless of how it is marketed.
Are expensive serums better?
Sometimes, when the money goes into stabilisation or protective packaging. More often price reflects branding. Our comparison guide shows how to check.
What does “dermatologist tested” mean?
Only that a dermatologist was involved in a test. It does not tell you how many people took part or what was found.
Do I need different products for morning and night?
Only sunscreen is strictly a daytime product. Retinoids are usually applied at night because light degrades them; most other actives can go either way.
Will you review the product I use?
We do not review products on request, but we do read ingredient lists readers send in and sometimes use them, anonymised, in columns. Write to the desk.