Our take
Is Biguanide a Good Ingredient?
It's effective for broad-spectrum preservation at low levels, but a higher risk of irritation or sensitization, along with region-specific concentration limits, tempers its usefulness and keeps it at Fair. Performance depends on precise dosing and may not suit very sensitive skin.
What it does
Skin Benefits
Helps keep products usable for longer by resisting contamination and spoilage; sensitivity can vary by individual, and regulatory limits may apply by region.
Where you'll find it
Uses in Skincare & Cosmetics
Used at low levels in water-based formulas like toners, gels, and cleansers to maintain product freshness, and also found in wipes and leave-on lotions where strong preservation is needed.
Before you use it
Irritation and sensitization can occur, particularly in leave-on or high-exposure products, so patch testing is prudent for reactive skin. Some biguanide preservatives are subject to specific concentration limits in certain regions, so compliant use levels matter.