Theanine at a glance

  • Amino acid found primarily in green tea
  • Proven antioxidant and soothing benefits
  • Helps attract and hold water throughout skin’s uppermost layers
  • Also used as a flavor enhancer in foods and beverages

Theanine description

Theanine is an amino acid that has emollient, humectant, and soothing properties on skin. It can be lab-synthesized but also occurs naturally in green tea leaves and some types of edible mushrooms. Consumption of green tea has numerous studies supporting its benefits for overall health and vitality, and its theanine component is of strong worth for use in skin care, too. Its low molecular weight allows it to penetrate past skin’s surface, where it works within its epidermal layers to attract and hold water, thus maintaining skin’s hydration. It also works within skin’s uppermost layers to offset factors that lead to signs of inflammation. Theanine is used on its own in foods and caffeinated beverages to enhance flavor (it tastes of caramel which offsets the bitterness of caffeine). As such, it is considered safe for use on skin although usage levels of theanine in cosmetics haven’t been established.

Theanine references

  • Frontiers in Nutrition, April 2022, pages 1–12
  • Frontiers in Pharmacology, July 2021, pages 1–14
  • Phytotherapy Research, March 2019, pages 571–583
  • Chemical-Biological Interactions, March 2018, pages 69–79
  • Journal of the Science of Food and Agriculture, August 2011, pages 1,931–1,939

Peer-reviewed, substantiated scientific research is used to assess ingredients in this dictionary. Regulations regarding constraints, permitted concentration levels and availability vary by country and region.

Ingredient ratings


Proven and supported by independent studies. Outstanding active ingredient for most skin types or concerns.


Necessary to improve a formula's texture, stability, or penetration.


Generally non-irritating but may have aesthetic, stability, or other issues that limit its usefulness.


There is a likelihood of irritation. Risk increases when combined with other problematic ingredients.


May cause irritation, inflammation, dryness, etc. May offer benefit in some capability but overall, proven to do more harm than good.


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Not rated

We have not yet rated this ingredient because we have not had a chance to review the research on it.