kojic acid

Kojic acid has a controversial history but new formulations are effective at reducing hyperpigmentation and dark spots

Posted by for Skincare

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Pop on your lab coat – it’s time to learn about kojic acid.

Over the course of the pandemic, I think it’s fair to say we all became bathroom chemists, of sorts. Where before a routine may have consisted of a trusted cleanser, toner and moisturiser, knowing the ingredients each formulation contained was probably a bridge too far. Now, we’ve become au fait with the name of individual acids, which moisturising agents work best for our skin and how to combine active ingredients to treat certain conditions. 

And, while some of us went slightly too far and found out what happens when you rush into using retinoids (retinol purge, anyone?) or the symptoms of a damaged skin barrier, the transparency of knowing exactly what works for our skin is refreshingly empowering. One such ingredient edging onto centre stage in recent months is kojic acid. 

What is kojic acid?

Designed to prevent the creation of melanin, kojic acid can be used topically to treat post-inflammatory hyperpigmentation, melasma and dark spots on the skin. Melanin – the pigment that gives eyes, hair and skin colour – is present in every human. Different levels of melanin denote light or dark pigmentation. A skin-brightening acid, kojic acid is a chemical product obtained from different types of fungi and is a byproduct of certain fermentation processes.

Historically, kojic acid has been a key ingredient in skin-whitening products – used at higher percentages and combined with arbutin to “bleach” the skin. However, when used in appropriate concentrations, it can be a potent way to treat specific melanin-related conditions without bleaching or whitening the surrounding skin. It’s deemed a well-tolerated alternative to hydroquinone, which can cause adverse reactions in dark skin tones.

Found to be safe for regular use at a strength of 1% or below, kojic acid can be found in cleansers, toners, serums and masks. 

How does kojic acid treat dark spots and hyperpigmentation?

OK, let’s break down the science

Melanin, a pigment containing cell, is produced by melanocytes and is transported to the top layer of the skin through a conversion process. Tyrosinase – a copper-containing enzyme – is the first step in this conversion process. 

When exposed to UV light (the sun), tyrosinase is made more active, however, kojic acid is able to “capture” said copper iron and prevent it from activating – thus reducing the amount of melanin produced in exposure to UV light.

Possible side effects of using kojic acid

“Contact dermatitis (especially for sensitive skin) is the main side effect of kojic acid which is accompanied by irritation, rashes, inflamed skin, itchiness and pain. These side effects can be observed with a higher concentration of more than 1% of KA. Another adverse reaction may appear in long-term use of kojic acid, such as sunburn in sensitive skin,” reads a 2019 study into the cosmetic application of kojic acid.

If you experience said side effects, stop usage until your skin returns to baseline and explore options suitable for your skin type. Lactic acid and other PHAs (polyhydroxy acids) are gentle alternatives suitable for sensitive skin.

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