Evidence & timelines

Articles

Long-view answers to "is this normal, and when does it stop" — the questions a single before/after photo can't answer.

• Does tretinoin work? A week-by-week timeline

  What actually changes, week by week, when you start tretinoin — and why the honest answer is 'track your own baseline,' not a fixed calendar.

  July 29, 2026

• The purge timeline: what to expect when skin gets worse before better

  What a "purge" is, roughly how long it tends to last, how it differs from a bad reaction, and how to tell the difference in your own record instead of guessing.

  July 29, 2026