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Ingredient glossary

Threonine

What Threonine does for your skin, who it suits, and what to watch for.

INCI: Threonine · Also: L-Threonine

Minor player

In short: Threonine delivers hydration and conditioning, suits most skin types, and the evidence behind it is limited.

What it does
Hydration, conditioning
Best for
Most skin types
Evidence
Limited
Does it clash with what you use? Check it →

Written by Maya FaourHow we score →

The molecule

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The Glow take

Nice to have, and nothing to overthink.

Threonine plays a quiet supporting role, rounding out a formula rather than being the reason you buy it.

— Maya

What it does

  • hydration
  • conditioning

weak evidenceMeasured among the NMF amino acids but not a major one, and no published study tests threonine alone on skin for any outcome. CIR judged the alpha amino acids safe as used.

Who it's for, and who should skip it

Tends to suit

  • dry
  • dehydrated
  • normal

Approach with care

No specific group flagged to avoid it.

  • Clogs poresLow
  • Irritation riskLow

How it fits each skin type

  • DrySuits
  • CombinationSuits
  • OilySuits
  • SensitiveSuits

Where it fits in your routine

WhenMorning and evening
Where in the orderOn damp skin, before your moisturizer

Plays well with

Threonine, answered

Is Threonine safe during pregnancy?

Yes. Threonine is considered safe to use during pregnancy and breastfeeding. As with anything, if you are unsure it is worth a quick word with your doctor or midwife.

Who should avoid Threonine?

No specific group is flagged to avoid Threonine. It is well tolerated by most skin. Still, introduce anything new one product at a time.

What concentration of Threonine actually works?

Its concentration is rarely printed on the label, so use the ingredient list as your clue: near the top third it is likely doing real work, near the bottom it is more of a sprinkle.

This, for every label you own

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Sources & how we reviewed this

  1. PMID 24335967abstract only, the full text is paywalled
  2. DOI 10.1038/s41598-019-54454-xabstract only, the full text is paywalled

Last reviewed August 2026. Educational information about a cosmetic ingredient, not medical advice.