Kojic acid is a fine white powdery substance composed of tiny crystals. The formal discovery of kojic acid occurred in 1989, and since then, the substance has been used widely in skin care products due to its numerous benefits. The ingredient is obtained from mushrooms that are native to Japan and is a by-product of the fermentation process used to produce the alcoholic beverage sake.
In skin care products, kojic acid functions primarily as a skin-lightening agent. To understand kojic acid's effects, it is necessary to understand how the skin gets it color. The body naturally produces a pigment known as melanin through specialized cells known as melanocytes. A person's genes determine how much melanin the body naturally produces. In people with fair skin, only small amounts of melanin are manufactured by the melanocytes, while copious amounts of the pigment are made by the cells of those with dark complexions.
The production of melanin in the skin does not occur in fixed amounts. Often, the cells produce more melanin in response to the environment or internal conditions in the body. When the skin is exposed to ultraviolet radiation from the sun, the melanocytes increase their production activities, causing the skin to tan. Repeated exposure to the sun can result in a permanent increase in melanin production in spots on the skin, causing small freckles and larger sun or age spots to form.
Melanin production can also increase when the skin becomes chronically inflamed. This is a common problem among acne sufferers who have prolonged discoloration of their skin after their acne blemishes heal. Hormonal changes that occur in the body during pregnancy can also spur melanin production, leading to a discoloration on the face that is known as melasma or chloasma. The overproduction of melanin caused by inflammation and hormonal activity typically declines over time, resulting in a gradual fading of the darkened skin.
When kojic acid is applied to the skin in concentrated amounts, the chemicals in the ingredient work on the melanocytes, interfering with the production of melanin. The exact way in which kojic acid lessens melanin production is not known, but many experts believe that the ingredient prevents an enzyme known as tyroinase from beginning the reactions in the cells that are necessary for manufacturing the pigment.
Prior to the discovery of kojic acid, the ingredient hydroquinone was largely the only ingredient used for skin whitening. Hydroquinone is known to cause skin irritation in many individuals, and for these people, dermatologists often recommend kojic acid as an alternative method for treating skin discoloration. Those with very sensitive skin may still develop redness or itching from the use of kojic acid, but overall, the ingredient is better tolerated than hydroquinone. The effects of kojic acid have been reported as being identical to those of hydroquinone or slightly less noticeable.
In addition to its skin-lightening abilities, kojic acid is classified as an antioxidant. This class of nutrients has the ability to counteract the effects of particles in the air called free radicals, which have the potential to cause oxidative damage to the skin cells. By limiting the effects of free radicals, kojic acid helps to prevent the formation of signs of aging that occur when the cells that produce the skin's vital structural proteins become damaged.
Kojic acid is also an antibacterial agent, meaning that it interferes with the processes that bacteria cells must perform to thrive and reproduce. By disrupting these processes, kojic acid causes the death of bacteria. Some dermatologists recommend the use of mild concentrations of kojic acid for addressing acne blemishes, which are often caused by bacterial infections in the pores.
When used in skin care products, kojic acid is a largely unstable compound and has the potential to turn brown if it is not stabilized by additional ingredients. As a result, some skin care companies use a more stable derivative of kojic acid known as kojic dipalmitate in place of the ingredient. Consumers should be aware that studies have not found kojic dipalmitate to be as effective in lightening the skin as kojic acid, so products that contain this version may not be as beneficial for treating hyperpigmentation.
Since the discovery of kojic acid, conflicting studies have been reported about the long-term safety of the ingredient. Results in some clinical trials have established a link between the ingredient and some forms of cancer, while others have found that kojic acid has no carcinogenic effects. Experts do generally agree that any cancer-causing properties of kojic acid would only be problematic if the body was exposed to large quantities of the ingredient. These levels greatly exceed the amount of kojic acid that is actually found in skin care products.