Laureth-4

Laureth-4 is an ethoxylated nonionic surfactant/solubilizer used in cleansers and as a penetration enhancer, typically around ~1–10% (and sometimes higher in rinse-off systems), where it can disrupt stratum corneum lipids and increase transepidermal water loss. Clinically, ethoxylated lauryl/laureth surfactants show meaningful irritancy in patch testing and are a common trigger for stinging/burning in eczema-prone or barrier-compromised skin, especially with repeated exposure in multi-step routines. Given its barrier-disruptive potential and the heightened risk in sensitive populations, it warrants a significant irritancy rating. Safety Notes: Laureth-4 is most often used as a nonionic surfactant/solubilizer and penetration-aid in leave-on lotions/serums and cleansing oils at low levels (~0.05–1%), where it helps solubilize fragrance/oils and improve sensory without overt detergency. In rinse-off cleansers, makeup removers, and emulsified cleansing oils/balms, it commonly runs ~1–10% as part of the surfactant system; the highest consumer-available levels are seen in anhydrous/emulsifying cleanser concentrates and niche high-solubilizer formulas where Laureth-4 can reach ~15–25% to self-emulsify oils and remove heavy makeup. There is no specific EU/FDA maximum concentration limit for Laureth-4 as such (it is generally governed by overall product safety/irritation potential), so the practical upper bound is set by tolerability and formula performance, with leave-on products typically staying much lower than rinse-off.

Suitability