Iodopropynyl Butylcarbamate

Iodopropynyl Butylcarbamate (IPBC) is a preservative typically used at very low concentrations (~0.01–0.1%), but it has well-documented potential to cause irritation and, more importantly, allergic contact dermatitis in leave-on products and compromised skin. Patch-test data and clinical reports place it among preservatives with a meaningful sensitization risk, so in sensitive or eczematous patients it warrants caution and patch testing. Given routine multi-product exposure and the stakes in reactive skin populations, it is best scored as a notable irritant/sensitizer despite its low use level. Safety Notes: In consumer cosmetics, iodopropynyl butylcarbamate (IPBC) is typically used at very low levels (around 0.001–0.005%) as part of preservative blends in leave-on products (creams, lotions, serums) and lower-water systems, reflecting both efficacy data and sensitization/iodine-related constraints. The highest over-the-counter levels observed are in rinse-off products (shampoos, body washes, cleansers) where formulas can legally/typically support up to ~0.02% in major markets (e.g., EU), and a subset of “high-preservation” or micro-challenging rinse-off products reach this upper end. Leave-on products generally top out much lower than rinse-off due to regulatory limits and irritation/sensitization risk.