Research Summary
Cyclic and linear siloxanes are compounds synthesized from silicon, consisting of alternating atoms of silicone and oxygen [Si-O] units with organic side chains. The most common cyclic siloxanes include octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6). The most common linear siloxanes are high molecular weight polydimethylsiloxanes (PDMS) and low molecular weight volatile linear siloxanes known as hexamethyldisiloxane (L2), octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), and dodecamethylpentasiloxane (L5).
These compounds exhibit low dermal toxicity, are generally inert and non-reactive, and are compatible with a wide range of chemicals, offering several beneficial properties. These properties include wash-off or transfer resistance from the skin, enhancement of sun protection factor (SPF), and emolliency in cleaning products. Due to these properties, siloxanes are incorporated into numerous consumer products, such as cosmetics and healthcare products, with over 300,000 tons annually sold into the personal care and consumer products sector.
Given their widespread use and potential for human dermal exposure, a comprehensive understanding of the dermal absorption and overall fate of siloxanes following dermal exposure is crucial. This review summarizes the available data regarding dermal absorption, penetration, and the fate of the most commonly used siloxane substances.
Keywords: Siloxanes, dermal, absorption, linear, cyclic, cosmetics, sunscreen products.
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