Soybeans, which come from the Glycine soja plant, are a rich source of isoflavones. Isoflavones are a class of phytoestrogens found in legumes and beans. Phytoestrogens have a structure that is similar to estradiol, which enables these compounds to have a weak estrogenic effect. Topical application of estrogen is known to increase skin thickness, thus, applying soy isoflavones may be beneficial for postmenopausal women who develop a thinner dermis due to decreased estrogen levels.

Soy isoflavones in skin care products can also be used to treat hyperpigmentation disorders. They are able to inhibit melanosome transfer, which means they prevent melanin from adhering to skin cells, therefore helping with blotchiness and discoloration. However, since this ingredient is a phytoestrogen it is not recommended for melasma treatment since melasma is somewhat estrogen mediated. Lastly, the soy isoflavones genistein and daidzein are known to have potent antioxidant and anti-inflammatory properties.