Isoleucine
molecular structure · PubChem
AKA: L-isoleucine, 73-32-5, (2S, 3S)-2-Amino-3-methylpentanoic acid, 2S, 3S-Isoleucine, (S)-Isoleucine, (S, S)-Isoleucine, 2-Amino-3-methylvaleric acid, Erythro-L-Isoleucine, L-Ile
Synthetic
Skin Conditioner
Hair Care
Amino Acid
Clean
L-Isoleucine; DL-allo-Isoleucine; 2-Amino-3-methylpentanoic acid
Effective at 0.04%
Solubility 34400
Formula
C6H13NO2
Mol. Weight
131.17
CAS #
73-32-5, 443-79-8
Form
Powder
State
Waxy shiny solid; [Merck Index] White solid; [Sigma-Aldrich MSDS]
Functions
Antistatic
Hair Conditioning
A catch-all term for ingredients that improve how skin looks and feels — softer, smoother, more supple. The workhorse behind most moisturizers.
Skin Conditioning
A catch-all term for ingredients that improve how skin looks and feels — softer, smoother, more supple. The workhorse behind most moisturizers.
Locks in moisture
Traditional Use
Essential amino acid identified in the early 20th century. Historically used in skincare formulations primarily for its protein-supporting properties, though not traditionally applied topically in cosmetics.
EWG
1
CIR
Safe as used
Pregnancy
Yes
CIR Safety Findings
Not Phototoxic
medical-approval
all-shades-safe
Concentration Guide
3e-05%
0.07%
0%100%
Reported use
CIR reported use: 0.00009-0.05 | 0.00003-0.07 | 0.0003-0.002
Regulatory Agencies
Skin Types
●all-skin-types
Best For
Dehydration
Pregnancy & Breastfeeding Safe
Yes
The paper trail
🔬Peer-reviewed1 paper →
⚖️Regulatory1 listing →
🛡️Safety-assessed2 reviews →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
Verified Jun 2026
Data: PubChem · CosIng · EWG · CIR