As glycolic acid has the smallest molecular weight of all the AHAs, it's fast acting, hence its popularity among dermatologists and skincare obsessives. But its potency can sometimes prove problematic, especially on darker skin tones, something Nicolas Travis, founder of Allies of Skin, recently flagged. So should those with darker skin tones try to minimise the use of glycolic acid – and perhaps AHAs altogether? Dija Ayodele , facial aesthetician and founder of the Black Skin Directory doesn’t think so, but advises proceeding with caution. "Glycolic acid is suitable for dark skin, but the problem lies in overuse. People are buying professional grade treatments online, with a low pH and high acid content, but don’t know how to use them correctly." This, she explains, can exacerbate the problem they’re trying to deal with in the first place. "If you’re looking to clear up discolouration in darker skin tones, overuse of AHAs can cause the skin to react, leading to post-inflammatory hyperpigmentation – so you end up going around in circles."