Threonine
INCI: THREONINE
Reviewed by Kate · Last updated 14 Aug 2026
An amino acid that supports skin hydration and structural integrity
Best For Skin Types
All, Dry, Sensitive
Addresses
Usage Frequency
Daily
Threonine products at Skintique
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What Is Threonine?
Threonine is a proteinogenic amino acid—one of the building blocks your body cannot synthesise on its own, meaning it must be obtained through diet or topical application. In skincare formulations, it functions as a humectant and conditioning agent, helping to draw moisture into the skin and support the skin's natural protein matrix.
When applied topically, threonine works alongside the skin's own amino acid pool to support hydration and maintain the structural integrity of the stratum corneum (the outermost layer of skin). It is commonly found in hair and scalp care products as well, where it helps condition and smooth the hair fibre.
Benefits for Your Skin
How It Works
Threonine is hygroscopic, meaning it draws water molecules from the deeper layers of skin and the environment into the stratum corneum, improving hydration at the surface. This hydrating effect is thought to plump the skin slightly and create a smoother appearance.
Additionally, as an amino acid, threonine is a precursor to proteins and peptides that form part of the skin's structural matrix. By supplementing the skin's own amino acid stores topically, formulations containing threonine may help maintain skin resilience and support natural renewal processes, though the extent to which topically applied amino acids integrate into the skin's protein synthesis remains an area of ongoing research.
Clinical Evidence & References
Research into skin metabolism suggests that amino acids play an important role in supporting healthy skin cell function and maintaining skin homeostasis, particularly in inflammatory or stressed skin states. However, specific clinical evidence for threonine's effects when applied topically to human skin is limited. Most existing data on this ingredient comes from its use in hair care formulations, where its conditioning properties are well documented.
The ingredient is considered safe and well-tolerated in skincare, and its humectant properties align with established skincare science, but rigorous randomised controlled trials specifically measuring threonine's impact on skin hydration or elasticity would strengthen the evidence base.
How to Use
Threonine-containing products can be used daily as part of your regular skincare routine. It works well in serums, moisturisers, and targeted treatments. There is no need to use it in isolation; it performs best as part of a comprehensive formulation that may also include other humectants (such as glycerin) and occlusives (such as ceramides) to seal in hydration.
Safety & Precautions
Frequently Asked Questions
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