Serenoa repens (saw palmetto) extract is a lipido-sterolic concentrate rich in free fatty acids (primarily lauric, oleic, myristic, and palmitic acids) and minor phytosterols. In vitro and ex vivo data indicate this lipid fraction can inhibit both type-1 and type-2 5-α-reductase, the enzymes that convert testosterone to dihydrotestosterone (DHT). By helping moderate the DHT axis in sebocytes, saw palmetto is frequently positioned as an “oil-control support” active for shiny or congestion-prone skin. Beyond sebum balance, the extract demonstrates antioxidant and anti-inflammatory behaviors reported in dermatology literature (e.g., modulation of COX-2/5-LOX pathways), which formulators leverage in lightweight emulsions and gel-creams designed to visibly calm redness while maintaining a non-greasy sensorial profile.

Because the scalp’s 5-α-reductase activity and inflammatory milieu strongly influence oiliness and scalp comfort, S. repens is increasingly included in rinse-off and leave-on scalp serums, micellar shampoos, and balancing conditioners. The ingredient’s primary cosmetic value here is supporting healthy sebum levels and scalp comfort. In practical formulation terms, its fatty acid profile also imparts mild emolliency, improving slip and after-feel in hydroalcoholic toners, oil-in-water emulsions, and anhydrous scalp oils.