Equol at a glance

  • A potent antioxidant that’s a by-product of soy isoflavone daidzein
  • Oil-soluble nature makes it highly bioavailable to skin
  • Interrupts pathways in skin’s surface that lead to loss of density and suppleness
  • Connects with specific receptor sites on skin’s surface to send healthy messages

Equol description

Equol is a metabolite (by-product) of the soy-derived isoflavone ingredient daidzein. It is a potent antioxidant, with comparative studies showing it has superior free radical-scavenging abilities when measured against vitamins C, E, astaxanthin and quercetin. This doesn’t mean equol is the best antioxidant, but it’s encouraging news for environmentally vulnerable skin, such as occurs with advancing age. In essence, equol helps strengthen skin so it’s better able to resist signs of aging. One of the ways equol is believed to work so well as an antioxidant is that it plays a role in interrupting multiple steps in what researchers describe as a cascade of oxidative damage. Equol also helps skin build up its own antioxidant defense system which ordinarily weakens with age and sun damage. All of this also has a pronounced soothing effect on skin’s surface, visibly calming irritated skin. There are two types of equol, known as R-equol and S-equol. The type of equol most often used in skin care is known as racemic equol, meaning it is an even mix of both types. This is the type of equol that has the most research supporting topical application and is considered more effective. Equol is an oil-soluble antioxidant that research has shown is highly bioavailable to skin, where it connects with specific receptor sites on skin’s surface. From here, it helps signal skin to look younger and smoother. Effective concentrations of equol in skin care are between 0.3–0.5%. Equol is considered safe for topical use since its parent compound daidzein has a long history of safe use in foods people routinely eat, such as soy (except the oil), dairy products (from cows fed a soy-rich diet), cabbage, nuts, grapefruit, grapes/raisins, and currants. The digestive process breaks down isoflavone daidzein to form s-equol, which has wide-ranging health benefits in the body.

Equol references

  • Journal of Functional Foods, August 2021, pages 1–8; and August 2019, pages 380–393
  • International Journal of Molecular Sciences, October 2021, pages 1–26
  • Current Pharmaceutical Design, December 2020, pages 5,837–5,843
  • Dermatologic Therapy, November 2020, pages 53–69
  • International Journal of Cosmetic Science, October 2017, pages 535–542
  • Ageing Research Reviews, August 2016, pages 36–54
  • Biofactors, January-February 2012, pages 44–52

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