Potassium Thiocyanate

Potassium thiocyanate is an inorganic thiocyanate salt used infrequently in cosmetics (more often as a chemical reagent), and salts like this can be irritating to skin and especially to eyes/mucosa at the concentrations needed to function. Human irritation data in routine skincare use is limited, and given its potential for stinging/irritant contact dermatitis in compromised barriers, I score it as a notable-risk ingredient requiring cautious use and patch testing. Safety Notes: Potassium thiocyanate is an uncommon cosmetic salt, but it appears at trace-to-low levels in niche leave-on serums/creams (often as part of antimicrobial/enzyme-supporting or “saliva/lactoperoxidase-system”-inspired concepts), where it is typically used around 0.001–0.1% due to irritation potential and the desire to limit thiocyanate load. Higher-strength consumer-available products that explicitly include thiocyanate as an active/functional salt have been observed up to about 1–2% (usually water-based leave-on treatments), with rinse-off formats generally staying toward the lower end because performance can be achieved with less contact time. There is no widely used, harmonized cosmetic maximum specific to potassium thiocyanate in major regulations, so market maxima are primarily constrained by tolerability, odor/taste considerations, and overall formulation safety assessments.