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Isobutyl Stearate
AKA “2-Methylpropyl octadecanoate, Octadecanoic acid, 2-methylpropyl ester, Stearic acid, isobutyl ester, isobutyl octadecanoate, HSDB 2177, UNII-V8DPR6HNX3, V8DPR6HNX3, Stearic acid isobutyl ester, Uniflex IBYS”
Emollient
Ingredient Facts
Isobutyl stearate
AKA: 2-Methylpropyl octadecanoate, Octadecanoic acid, 2-methylpropyl ester, Stearic acid, Isobutyl ester, Isobutyl octadecanoate, HSDB 2177, UNII-V8DPR6HNX3, V8DPR6HNX3, Stearic acid isobutyl ester, Uniflex IBYS
Emollient · Emollient · EWG: 1
Plant-Derived
Emollient
Skin Conditioner
Clean
The CIR Expert Panel concluded that the alkyl esters, listed subsequently, are safe in the present practices of use and concentration described in this safety assessment when formulated to be non-irritating.
Effective at 21.5%
Solubility Very sol in ether
Formula
C22H44O2
Mol. Weight
340.60
CAS #
646-13-9
Form
Liquid
See origin →
Functions
Skin Conditioning
A catch-all term for ingredients that improve how skin looks and feels — softer, smoother, more supple. The workhorse behind most moisturizers.
Emollient
Fills in the tiny cracks between skin cells to make everything feel smooth and soft. The "silky finish" ingredient.
Locks In Moisture
Traditional Use
Synthetic ester developed as a cosmetic emollient in the mid-20th century. Created to mimic the conditioning properties of natural stearic acid while offering better stability and absorption in cosmetic products.
Skin Types
●all-skin-types
Best For
Dryness
Pregnancy & Breastfeeding Safe
Yes
EWG
1
CIR
Safe as used
Pregnancy
Yes
CIR Safety Findings
Not a Sensitizer
medical-approval
all-shades-safe
Concentration Guide
0.0008%
43.0%
0%60%
Effective Range
CIR reported use: 0.0008-12 | 0.002-43
Regulatory Status
USA✔ permitted
EU⚠ restricted
JAPAN⚠ restricted
CANADA⚠ restricted
Amended Final Report on the Safety Assessment of Hydroxystearic Acid
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Final Report on the Safety Assessment of Butyl Stearate, Cetyl Stearate, Isobutyl Stearate, Isocetyl Stearate, Isopropyl Stearate, Myristyl Stearate, and Octyl Stearate
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Final Report on the Safety Assessment of Isostearic Acid
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Final Report on the Safety Assessment of Oleic Acid, Lauric Acid, Palmitic Acid, Myristic Acid, and Stearic Acid
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Final Report: Safety Assessment of Polyhydroxystearic Acid, Poly(3-Hydroxyoctanoic Acid, and Polylactic Acid as Used in Cosmetics
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
Re-evaluation: Safety Assessment of Hydroxystearic Acid as Used in Cosmetics
Cosmetic Ingredient Review (CIR) Expert Panel
International Journal of Toxicology
→
10-Hydroxystearic Acid
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Isobutyl Stearate
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Polyhydroxystearic Acid
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Stearic Acid
European Commission
EU Cosmetic Ingredient Database (CosIng)
→
Hydroxystearic Acid
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Isobutyl Stearate
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Isostearic Acid
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Polyhydroxystearic Acid
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Stearic Acid
Environmental Working Group (EWG)
EWG Skin Deep Cosmetics Database
→
Simultaneous contact sensitivity to hydroxystearic acid and C18-36 acid triglyceride in lip glosses.
Kimura M, Kawada A, Ogino M, Murayama Y
Contact dermatitis, 2002
→
Microemulsions based on TPGS and isostearic acid for imiquimod formulation and skin delivery.
Pescina S, Garrastazu G, Del Favero E, Rondelli V, Cantù L et al.
European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences, 2018
→
Bio-derived hydroxystearic acid ameliorates skin age spots and conspicuous pores.
Schütz R, Rawlings AV, Wandeler E, Jackson E, Trevisan S et al.
International journal of cosmetic science, 2019
→
Bio-derived hydroxystearic acid ameliorates skin age spots and conspicuous pores.
Schütz R, Rawlings AV, Wandeler E, Jackson E, Trevisan S et al.
International journal of cosmetic science, 2019
→
Bio-derived hydroxystearic acid ameliorates skin age spots and conspicuous pores.
Schütz R, Rawlings AV, Wandeler E, Jackson E, Trevisan S et al.
International journal of cosmetic science, 2019
→
Verified Jun 2026
Data: PubChem · CosIng · EWG · CIR