Tretinoin
A prescription medicine in Korea. In a 1991 trial of 251 people, 79% of those using 0.05% for 24 weeks improved against 48% on vehicle. But in a 29-person trial in 2022, active and vehicle both improved 30–40% and could not be told apart.
Benzoyl Peroxide
A network meta-analysis of 179 randomised trials and about 35,000 observations found that the most effective topical option for mild-to-moderate acne was a retinoid combined with benzoyl peroxide, reducing lesion counts by 26.16% more than placebo. In Korea, single-ingredient products are available over the counter.
Adapalene
All 12 products registered in Korea are prescription-only. In a 67-person split-face trial, adapalene 0.3% with benzoyl peroxide 2.5% reduced scar counts by 15.5% over 24 weeks while the vehicle side increased by 14.4%.
Azelaic Acid
All six products registered in Korea are over the counter. In a Cochrane review, azelaic acid beat placebo on participants' own assessments (three trials pooled, risk ratio 1.52), and a phase 3 trial of a 15% foam also beat vehicle. The review noted that most included studies were at high or unclear risk of bias.
Eflornithine
In a vehicle-controlled, double-blind trial alongside laser (31 people), complete or almost complete hair removal reached 93.5% and all three endpoints were significant. In a separate 22-person trial of maintenance after IPL, regrowth fell 14% at one month and 17% at six — but the three-month point was not significant.
Finasteride
In male pattern hair loss, two trials in 1,553 men and a Japanese trial in 414 all beat placebo. Hair counts, investigator assessment and a blinded expert photographic panel all pointed the same way, and the placebo groups went on losing hair. But in a trial of 137 postmenopausal women there was no effect. And in a meta-analysis pooling 15 placebo-controlled trials and 4,495 subjects, the relative risk of sexual adverse effects was 1.66 (95% CI 1.20–2.30).
Hydroquinone
It is the name that appears most often as a comparator on this site, and not one trial here was designed to measure hydroquinone. All three were designed to measure something else, with hydroquinone as the control arm. What that arm did: 4% cream lowered the melasma score (mMASI) by an average of 33% over 90 days (95% CI 23–42%). And it did not differ significantly from thiamidol, cysteamine or tranexamic acid.
Isotretinoin
We could not put a trial comparing its effect size against placebo on this page. This drug was established in the 1980s, and almost every randomised trial since asks how much, not whether. And on that question two reviews came apart: reading the same four trials, a 2023 review wrote that low dose is preferable, while a 2026 meta-analysis wrote that neither regimen was favoured (p = 0.15). And this page gives one of its badges to pregnancy — even with a prevention programme, there were 3.4 pregnancies per 1,000 courses.
Spironolactone
Pooling five placebo-controlled randomised trials in 563 patients, the odds of investigator-assessed acne improvement were 6.59 times higher (95% CI 3.50–12.43), with almost no disagreement between trials (I² = 0%). But the pooled patient-rated assessment was not significant (OR 5.22, CI 0.62–44.24, I² = 85%). And the primary outcome of the 410-patient British SAFA trial was a patient-reported quality-of-life score at 12 weeks, where the difference of 1.27 (CI 0.07–2.46) barely cleared zero. At 24 weeks it was 3.77 (2.50–5.03). That trial was paid for by British public research funding, not by a manufacturer.
Minoxidil
Vehicle-controlled trials: two in women (381 over 48 weeks, 404 over 24) and two in men (352 over 16 weeks, 90 over 36). In all four, 5% beat vehicle on hair count. But 2% did not differ from vehicle on the users' own assessment, 10% was not better than 5%, and oral minoxidil did not beat topical.
Whether and how to use it is decided with a doctor or pharmacist.
Ingredient Beauty Benefits