Lactic acid is derived from the bacterial fermentation of sugar. pH is important for both hair and skin, but particularly important for hair. Hair is comprised of three layers, with the outer layer called the cuticle. When the pH of the hair is too high (for example when using actual soap (not our shampoo bars- they're not soap)), the cuticle sticks up at an angle from the layer underneath leading to rough, dull hair. We use lactic acid to ensure our products are at the correct pH balance so your hair and skin are kept happy. Whilst the idea of using something created by bacteria might sound gross, it's much more environmentally friendly than the alternative- which is using coal or coal tar as the initial source. Our lactic acid is sustainably sourced, completely biodegradable and safe to use in the concentrations we use it for (and much higher.)