For how we live.
Pooled across 216 participants, the devices beat control by 45.3% on inflammatory lesions. The trials are small, none of the devices tested is necessarily one now sold, and the market is barely regulated.
Users were slightly less likely than non-users to attempt suicide in the two to four years after treatment. The FDA's 2005 boxed warning stands, and the analysis cannot explain the direction of the finding.
Two ingredients carry most of the real evidence. The rest of the multi-step routine adds cost and, when actives are layered too hard, a damaged skin barrier.
Tretinoin beats its own vehicle in randomised trials — though the vehicle does much of the work. In the few head-to-head trials against over-the-counter retinol, both arms improved and tretinoin irritated more.
A parental history of acne carries a pooled odds ratio of 2.91. Dairy carries 1.25, from observational studies with demonstrated publication bias — and diet appears nowhere in the treatment guideline.