Kojic’s acid primary use — and benefit — is to lighten visible sun damage, age spots, or scars. In this article, we look at how Kojic Acid is used, possible health benefits it might have, potential risks, and side effects.
What is Kojic Acid?
Kojic Acid is a common ingredient used in topical skin care products. It is primarily used to lighten or brighten skin. Cosmetic and skin care products that might contain Kojic Acid include:
Kojic Acid is also found in some fermented foods such as miso (soybean paste), shoyu (soy sauce), and sake. It is also used as a food additive to prevent browning. Let’s find out if Kojic Acid is right for you.
Where does Kojic Acid come from?
Kojic Acid can be found in a number of types of fungi, including Aspergillus, Acetobacter, and Penicillium. Chemically, Kojic Acid is considered an organic acid. It’s real, chemical name is 5-hydroxy-2-hydroxymethyl-?-pyron.
What does Kojic Acid do?
Kojic Acid lightens pigmentation in the skin. It does this by inhibiting melanin production in the skin. The process it uses is to inhibit an enzyme (tyrosinase) that is important to the production of melanin.1
What is Skin Pigmentation?
Human skin color is determined by a number of factors. Mainly
- Carotenoids: a reddish pigment found in vegetables. It reaches the skin carried through blood.
- Hemoglobin: found in blood that circulates in the skin. Hemoglobin is redder when it is oxygenated.
- Melanin pigment: various types are made in the skin.
Melanin is made in the skin through a process known as melanogenesis. It occurs in cells found in the skin called melanocytes. Melanocytes are located in the bottom layer (the stratum basale) of the skin’s epidermis.
One enzyme important in the process of melanogenesis is called tyrosinase. If we can biochemically block the activity of this enzyme (tyrosinase) we can block the production of melanin. This, in turn, would lighten skin. Kojic Acid inhibits tyrosinase by binding copper, an important cofactor of tyrosinase. Kojic Acid binds this copper making the enzyme ineffective at making melanin.
The purpose of melanin in the skin is to protect the cells and their DNA from UV light. Melanin levels also increase when the skin is exposed to UV light. We know this as a suntan.
In human sensitive skin, there are two different types of melanin: eumelanin (which is either black or brown form) and pheomelanin (which is red or yellow). The amounts and types of melanin are mostly determined by genetics.2
What is Hyperpigmentation?
Hyperpigmentation is a non genetic darkening of the skin. These skin discolorations can be a cosmetic concern for many people. What causes darkening of the skin? There are a number of things that include:
- Acne scars
- UV light (sunlight)
- Inflammatory conditions
Acne scars arise from increased pigment formation as a result of bacteria, oil, and inflammation of the skin. Hyperpigmentation from acne is more notable in people with darker pigmentation to start with.3
Melasma is a type of hyperpigmentation caused by hormones and often seen after pregnancy. It can also be caused by hormonal therapies such as oral contraceptives. It appears as patches on the face, usually the cheeks, bridge of the nose, forehead, chin, and upper lip, and rarely on other parts of the body. Hyperpigmentation caused by melasma is much more difficult to treat than other types of hyperpigmentation.4
Exposure to UV(ultraviolet) light or sunlight causes patches of darkened skin referred to as solar lentigo. UV radiation will cause local proliferation of melanocytes, stimulating increased melanin accumulation in the skin cells (keratinocytes). Solar lentigos are very common, especially in people over the age of 40 years.
Inflammatory hyperpigmentation can be caused by rashes, psoriasis, eczema, infections, allergic reactions, burns, or even some cosmetic procedures. Again, darker-skinned people can be more severely affected by inflammatory hyperpigmentation.
What is Kojic Acid used for and who can benefit?
Skin lightening is done to improve cases of hyperpigmentation or over and uneven pigmentation. It can lighten visible sun damage, age spots, or scars. It is not meant to lighten overall skin color. Lightening uneven pigment can result in an anti-aging effect on the skin. You can expect it to take 2 weeks of use before seeing noticeable results. Results can be increased with the use of an exfoliant like glycolic acid. Results are also not permanent and continued use is required.
Because it has antibacterial properties, Kojic Acid can also help control acne. Kojic Acid also has antifungal properties and has been used to help reduce yeast infections.
Is Kojic Acid Safe?
Because Kojic Acid is often produced during the fermentation of historically used foods, including Japanese sake, soy sauce, and miso, it has a long history of consumption. Toxicity resulting from an oral dose has not been reported, but convulsions may occur if Kojic Acid is injected.5,6,7,8
The Cosmetic Ingredient Review (CIR) has reviewed the toxicology reports on Kojic Acid and found it to be safe at a concentration of 1% when used topically.
In some products, however, it is used at much higher amounts. Because Kojic Acid has limited absorption into the skin this decreases both it’s toxicity as well as its activity.9
Current research is examining ways to make Kojic Acid more able to penetrate skin such as by attaching small peptides to the molecule. We soon may see various forms of Kojic Acid in skin care products in the future as a result of this research.
Side effects of Kojic Acid include dry skin, red rash, itching, irritation, and burning. Over time, long-term use of Kojic Acid may make your skin more susceptible to sunburn. If you experience facial redness, rashes, irritation, or pain when using Kojic Acid, stop using it immediately.10,11
Is Kojic Acid effective?
Kojic Acid as a therapy by itself has shown modest effectiveness. Its effectiveness increases in combination with other ingredients that include ascorbic acid (vitamin C), arbutin, and hydroquinone. Kojic Acid is an effective inhibitor of tyrosinase, however, its effectiveness in the skin is limited by its poor ability to penetrate the skin. Good clinical trials to determine the effectiveness of Kojic Acid are lacking.
How to use Kojic Acid?
Because Kojic Acid can cause some irritation it is best used in a wash-off product such as soap or a mask. Products with Kojic Acid are typically used on the face and hands but can be used safely on most parts of the body.
Kojic Acid is touted as the best antioxidant for skin but is more used as a skin brightening/ whitening agent. It is used at concentrations ranging from 0.1%to 2%. It is also an antibiotic and anti-inflammatory and has pain relief properties.
It can be used in foods as an antioxidant and additive to prevent browning.
Kojic Acid v Hyroquinone
Kojic Acid has been touted as an alternative to hydroquinone for skin lightening. Side effects of hydroquinone include skin irritation, sensitization, burning, stinging, dermatitis, inflammation, dryness, and redness. However, you might find a combination of the two to be more effective than use alone.12
Long-term use of hydroquinone can cause ochronosis which means the skin will darken further, making more hyperpigmentation.
If you are concerned about hyperpigmentation due to sunspots or acne, you may want to consult your dermatologist. A product that contains Kojic Acid may work well for you.