Alcohol.

What it does

It is a fast-evaporating solvent and penetration enhancer that dissolves ingredients which won't mix into water or oil, gives lightweight products a quick-drying, weightless feel, and acts as an astringent and mild antimicrobial. It is a formulation aid, not a skin-care active.

Benefits

• Dissolves actives and fragrances that resist water and oil, helping make thin, cosmetically elegant formulas
• Evaporates quickly for a fast-drying, weightless finish that many people like in toners and lightweight sunscreens
• Acts as a penetration enhancer, helping other ingredients absorb
• Has astringent and antimicrobial properties, which is why it is common in toners and oily-skin products

Side effects

• Can be drying or dehydrating, especially when it is among the first ingredients on the list or used frequently
• Pure ethanol irritates skin and eyes; high amounts can sting or aggravate sensitive or compromised skin
• Some experts argue regular exposure may disrupt the skin barrier and cause inflammation, though this remains a debated point

Who it's for