Whenever people say, “You can never have too much of a good thing,” they obviously did not consider the ingredientkojic acid. A skin brightener in nature, this organic acidhas been cleared by theCosmetic Ingredient Review Expert Panel to be used in cosmetic ingredients at the concentration of 4% or less, although it has been on the market since 1955. Depending on if thekojic acid product is intended to be washed off (or used on occasion) or absorbedby skindictateswhere the concentration should land.A good rule of thumb to avoid a possible allergic reaction, irritation, or rashis to keep concentrations around 1% to 2%. If a client has sensitive skin, kojic acid should be slowly introduced into their skin care routine, using the product once or twice a week at first. It should also be noted that long-term use of kojic acid can make any skin type more susceptible to sun damage. 

While it can be used with other brightening and exfoliating ingredients, thecoupling of products increases the chances of undue dryness and irritation, so it is recommended to gradually add additional products containing actives when already utilizing kojic acid. 

A hyperpigmentation superstar,kojic acid is the product of various types of fungi (such as A. flavus, A. oryzae, A. tamarii, and A. parasiticus) and is present in certain fermented, Asian foods, such as soy sauce, rice wine, and sake. It prevents the development of tyrosine, the amino acid responsible for the production of melanin. Because kojic acid works by prevention, it differs from the standard acid that breaks the bonds found between skin cells, stimulating exfoliation.

In addition to its cosmetic advantages, kojic acid has been used to create a nano-carrier system for anti-cancer drug delivery, it generates asubstantialpromotion of cellular turnover, and reduces the growth of tumors.

With its many uses and benefits, it is imperative to investigate the concentrations of kojic acid in any products being sold or used in a spa. Additionally, client education is always a must but is especially important when using active ingredients. Keep researching to bring clients the safest and most beautiful results.