Sorbitan Isostearate
Also known as Sorbitan Isostearate, Sorbitan monoisostearate, Isostearic acid, ester with sorbitan
“CIR Expert Panel says: safe as used in cosmetics.”
Sorbitan Isostearate is the ester of sorbitan and isostearic acid, functioning as a nonionic emulsifier and surfactant in cosmetics. The 2002 CIR safety assessment (PMID 12042063) evaluated it alongside nine other sorbitan fatty acid esters and concluded it is safe for cosmetic use under present practices of use and concentration. The assessment noted that while sorbitan isostearate showed moderate irritation in one rabbit study and mild-to-severe intradermal irritation in guinea pigs at elevated doses, it was nonsensitizing in clinical tests and the panel affirmed the unconditional Safe (S) finding — reflecting that typical formulation concentrations (generally below 10%) are well tolerated. The CIR Final Report was updated in December 2014, reaffirming the original safe conclusion.
Nonionic emulsifier compatible with a wide range of cosmetic ingredients
Provides skin feel and emulsion stability in leave-on formulations
Derived from isostearic acid (branched C18 fatty acid) — gives better cold-temperature stability compared to straight-chain sorbitan stearate
Unconditional CIR Safe (S) finding — no formulation restrictions required
- · Moderate dermal irritation observed in one rabbit study at high exposure; mild-to-severe intradermal irritation in guinea pigs — both at non-typical cosmetic use conditions
- · Historical cocarcinogen findings at high systemic doses noted in the CIR assessment; not relevant to typical topical cosmetic use
CIR Quick Reference Table (12/2017, revised 07/2018) — SORBITAN ISOSTEARATE row: Finding=S, Citation=IJT 21(S1):93-112, 2002; Final repor…
“Sorbitan Isostearate | S | | IJT 21(S1):93-112, 2002; Final report 12/2014 available from CIR”— QRT-122017revised072018.pdf, p. 125