Silybum Marianum Seed Oil

Silybum Marianum (milk thistle) seed oil is primarily an emollient lipid used at a few percent to higher levels in moisturizers, and as a non-volatile oil it is generally well tolerated with low intrinsic sting potential. However, like other botanical seed oils it can contain minor unsaponifiables/trace proteins and oxidation byproducts that occasionally trigger irritant or allergic contact dermatitis in highly reactive or eczema-prone patients, especially in compromised barriers. Given this low-but-real risk in sensitive populations, it fits best as a gentle ingredient rather than exceptionally gentle. Safety Notes: In commercial skincare, Silybum Marianum (milk thistle) seed oil is often used as a minor emollient/marketing botanical in leave-on creams, serums, and cleansers at very low levels (~0.01–0.1%), commonly within a broader plant-oil blend. Mid-range usage (~0.5–5%) appears in facial oils, barrier creams, and antioxidant-focused leave-on products where it contributes slip and unsaponifiables, while the top end includes consumer-available single-ingredient carrier oils sold as “100% milk thistle seed oil” or predominantly milk-thistle facial oils approaching 100%. No specific EU/FDA cosmetic maximum is set for this fixed oil; practical limits are driven by odor/feel, oxidation control, and compatibility in emulsions (leave-on typically higher than rinse-off).