Methicone

Methicone is a silicone-based emollient/skin protectant used at low-to-moderate levels to improve slip and reduce transepidermal water loss; it is chemically inert, non-reactive, and not pH-dependent. Human repeat-insult patch testing and broad clinical use of silicones show very low irritation and sensitization rates, with reactions being uncommon and typically related to individual intolerance or occlusive effects in very reactive skin. Given the need to account for compromised eczema-prone users while recognizing its overall excellent tolerability, it fits best as a very gentle ingredient rather than truly inert. Safety Notes: Methicone is used at very low levels (~0.05–0.5%) in many consumer leave-on products (lotions, sunscreens, primers, hair serums) primarily for slip, spreadability, and a light occlusive/sensory effect, often as part of a silicone blend. Higher levels are found in more silicone-forward cosmetics (primers, silicone gels/serums, scar-care style gels) where methicone can be a major emollient/feel agent, reaching the low-to-mid teens in OTC products. It is generally used in leave-on products more than rinse-off, where levels tend to stay in the low single digits due to deposition/rinse dynamics and cost.