Silybum Marianum Extract

Silybum Marianum (milk thistle) extract is primarily used as an antioxidant/soothing botanical, typically at low concentrations (often <1–2%) in leave-on products, and is generally well tolerated in clinical and consumer use. However, as a plant extract it contains multiple phytochemicals and can trigger irritation or allergic contact reactions in a minority of sensitized or highly reactive patients (including those with eczema or botanical allergies), so it cannot be scored as “very gentle” for all compromised skin. Safety Notes: In mass-market leave-on skincare (creams/serums/toners), Silybum marianum (milk thistle) extract is commonly included at very low supportive levels (~0.01–0.1%) as part of antioxidant/soothing blends, consistent with typical botanical extract dosing and supplier recommended use levels. Higher-strength consumer products (especially “antioxidant,” “detox,” or post-procedure-calming serums) can reach ~1–5% when the ingredient is a primary featured extract or supplied as a concentrated glycerin/butylene glycol extract; above this is uncommon due to solubility/appearance/odor and increasing formula instability or tack. Rinse-off products typically sit toward the lower end because of short contact time, while the upper end is primarily observed in leave-on formulations.