Every over-the-counter skincare claim, graded and plotted by evidence.

Zero clinical trials support facial tallow use. The "our ancestors used it" argument conflates cultural practice with clinical evidence. Highly comedogenic — likely worsens acne.

A handful of small human trials show modest hydration and wound-healing effects. Biological mechanism is plausible, but "overnight barrier repair" overstates what any single-ingredient serum can do.

Occlusion with petrolatum has decades of barrier-science support and modest RCT evidence for reducing transepidermal water loss. Works as claimed for dry skin — not appropriate for acne-prone skin.