How we write these answers.

Every answer starts with the pages that can actually settle the question: health services such as the NHS and the FDA, dermatology bodies such as the American Academy of Dermatology and DermNet, hospital health libraries, peer reviewed papers, and the brand's own product page for its ingredients and directions. Retailers, blogs and forums are left out, which removes most of the internet and almost none of the useful part.

Each answer is written from those pages, and every factual paragraph links to the pages it came from, numbered so you can check them yourself. Before a page goes up, every citation is checked against the text of its source, and the page needs at least two independent sources behind it. A page that cannot meet that bar is not published, however good the question is.

These pages explain skincare. They are not medical advice and they do not replace a doctor. If something worries you, or you are pregnant, nursing or using prescription treatment, ask a doctor or pharmacist before you change your routine.

If an answer is wrong or out of date, email hello@comfi.skin and we will correct it.