Propylene Carbonate

Propylene carbonate is primarily a solvent/penetration aid used at low percentages in cosmetics, and it is generally tolerated but not completely inert. Patch-test and safety reviews describe it as a mild irritant in some individuals (especially with occlusion or compromised barriers), with sensitization being uncommon. Given its solvent nature and the higher risk profile in eczema or post-procedure skin when combined with other actives, a mild irritancy score is the safest clinically-aligned assessment. Safety Notes: In consumer cosmetics, propylene carbonate is most often used as a co-solvent/viscosity reducer and delivery aid, where it appears at low levels (~0.05–1%) in leave-on serums/creams and color cosmetics to help solubilize lipophilic actives or improve spread. Higher levels (5–20%) are observed in OTC specialty products such as spot treatments, nail/lacquer-related cosmetics, and some high-solvent anhydrous systems where it functions as a primary solvent; above ~20% is uncommon in mainstream skincare due to sensory/irritation and formulation balance constraints. No specific EU/FDA concentration cap is generally assigned to propylene carbonate as a cosmetic ingredient, so market use is mainly limited by tolerability and product type (leave-on tending lower than rinse-off/solvent-heavy formats).