Isoleucine
Essential amino acid, isomer of leucine. In skincare – part of NMF amino acid cocktails, without a standalone claim. In keratinocyte studies isoleucine stimulates synthesis of beta-defensin-2, an antimicrobial peptide – but the clinical significance of this effect with topical application is not proven.
Evidence by route
Topical application
Safe component of amino acid complexes. Promising in vitro data on innate immunity stimulation have not yet been confirmed clinically.
- CIR Cosmetic Ingredient Review safety assessment.
How to read tiers A–F
- CWeak evidence. In vitro data, open-label studies, or expert consensus
Tolerability and safety
- Irritation potential
- Low
- Allergen risk
- Low
- Pregnancy
- Safe
- Suitable for
- Normal, Dry, Combination, Oily, Sensitive
About this ingredient
Isoleucine is an essential branched-chain amino acid, structural isomer of leucine. Enters the body only with food. Component of muscle proteins and neuropeptides. Where applied. Part of amino acid blends in NMF (Natural Moisturizing Factor) of creams, serums, toners (0.01-0.5%). In Spain in Sesderma Factor G, Filorga NCEF, Mesoestetic. Evidence base. On keratinocytes in vitro isoleucine stimulates synthesis of beta-defensin-2 – an antimicrobial peptide (Fehlbaum 2000, Schauber 2004). Potentially useful in atopic dermatitis and acne, but clinical significance with topical use is not proven. No direct RCTs on topical isoleucine. Safety. CIR rated isoleucine and other amino acids safe at cosmetic concentrations (2013). Inert, hypoallergenic. Pregnancy and lactation – safe topically. Suitable for all skin types.
Frequently asked questions
Is Isoleucine safe during pregnancy?
Isoleucine is considered safe during pregnancy at typical cosmetic concentrations. Systemic absorption through the skin is minimal.
What skin types is Isoleucine for?
Isoleucine suits: normal, dry, combination, oily, sensitive.
What is Isoleucine and what does it do in cosmetics?
Essential amino acid, isomer of leucine.
What's the INCI name for Isoleucine?
The INCI name is Isoleucine. It may also appear as: L-Isoleucine.
See Isoleucine in a product composition right on the store page
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