Fuller's Earth

Fuller’s Earth is an absorbent clay (typically used at high percentages in masks and cleansers) that can strongly degrease and dehydrate the stratum corneum, increasing tightness, stinging, and barrier disruption—especially in eczema-prone or compromised skin. While not a classic chemical irritant, its high oil-adsorption and potential for mechanical friction during application/removal make irritation and flares reasonably common in sensitive populations. Given real-world use as leave-on or semi-occlusive masks and the frequent cumulative dryness it adds to routines, a moderate score is warranted for patient safety. Safety Notes: In commercial products, Fuller's Earth (typically a smectite-rich clay used for oil absorption/cleansing) appears at very low levels (~0.1–1%) in leave-on lotions/creams and some wash-off cleansers as a mild mattifying/opacity-boosting absorbent. It is commonly used at moderate levels (~5–30%) in rinse-off masks and scrubs, and the highest consumer-available strengths are essentially “pure clay” powders or clay mask pastes sold OTC that are ~90–95% Fuller's Earth (with the balance being minor additives like botanicals, fragrance, or anti-caking agents). Extremely high levels are generally limited to rinse-off formats due to drag/whitening and stability/sensory constraints in leave-on products.