Isobutyl Stearate
AKA “2-Methylpropyl octadecanoate, Octadecanoic acid, 2-methylpropyl ester, Stearic acid, isobutyl ester, isobutyl octadecanoate, HSDB 2177, UNII-V8DPR6HNX3”
Synthetic
Ingredient Facts
Isobutyl stearate
AKA: 2-Methylpropyl octadecanoate, Octadecanoic acid, 2-methylpropyl ester, Stearic acid, Isobutyl ester, Isobutyl octadecanoate, HSDB 2177, UNII-V8DPR6HNX3
Synthetic · Emollient · EWG: 4
Plant-Derived Synthetic
Emollient
Skin Conditioner
Synthetic
Clean
A lightweight emollient that softens and smooths skin, leaving it feeling hydrated and conditioned without a greasy residue.
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
Melanin-Rich Skin
Suitable
Pregnancy & Breastfeeding Safe
Yes
EWG
4
CIR
Safe
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 Agencies
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 Feb 2026
Data: PubChem · CosIng · EWG · CIR