tracked every product switch for 1 year - here is what moved the needle

kept a log of every skincare change + a weekly skin score. net findings: - spf consistency: +big - tretinoin 0.025: +big (after purge) - 2.5% BHA 2x/wk: +small - vitamin C serum: nothing measurable - 10-step korean routine: negative (irritation) that's it. $$ on retinoid + spf, pass on the rest for me. ymmv obviously.