Sun exposure comes with a number of effects on your skin—not all of them positive. While the current beauty landscape is trending towards all things bronze and sun-kissed, too much time spent soaking up the rays can result in premature fine lines, skin cancer, and hyperpigmentation. Also known as dark spots, age spots, or liver spots, hyperpigmentation is caused by an overproduction of melanin and manifests as patches that are deeper in color than your natural skin tone. Aside from taking protective measures like using ample SPF and self-tanner products, existing dark spots can be lightened up with the help of kojic acid, a skin-care ingredient that’s seeing a surge in popularity thanks, in part, to social media.
Lately, a stream of citrus-hued soaps crafted using the acid has been flooding feeds, promising an easy-to-use means of brightening dark spots, melasma (hyperpigmentation caused by hormonal changes), and shadowy underarms.
But what exactly is kojic acid, and how effective is it?
“Kojic acid is a natural substance that is actually made from fungi commonly used in skin-care ingredients,” says dermatologist Dr. Chris Tomassian. The acid is a popular ingredient in serums, creams, and, most recently, soaps designed to combat hyperpigmentation. Once kojic acid penetrates the skin, it blocks the production of tyrosinase, an enzyme crucial for the production of melanin. The ingredient is a gentler answer to the lightening agent hydroquinone.
“Most of the time, kojic acid is formulated with other ingredients like tranexamic acid, niacinamide, and licorice root,” says Tomassian, who recommends using your chosen product twice daily for the best results. “Consistency and patience are key ingredients for improving unwanted dark spots,” agrees dermatologist Dr. Karen Kagha. “Hyperpigmentation can be stubborn, and often requires time and diligence to achieve your brightening goals.”
It’s the need for repetition and patience that makes Tomassian hesitant to recommend kojic acid soaps to those looking to treat drastic hyperpigmentation, primarily because the acid is so quickly rinsed from the treatment area. “Unless the product is really sitting on the skin for awhile it will not give the desired results,” he says. That said, because much of underarm darkening is due to skin and product build-up, pairing a kojic acid-imbued product with an exfoliating tool is likely to help—meaning that there is some validity behind kojic acid soap’s virality.