Like the rest of the skin on your body, the scalp sheds dead skin cells by pushing them outwards, where they eventually and naturally flake off. These flakes are normally very small and unnoticeable. However, dandruff occurs when this process happens more rapidly than the normal cycle, causing a build-up of more visible flakes.
The root cause of dandruff is from a naturally occurring microbe, which is found on everyone’s scalp, called Malassezia globosa. It feeds on the scalp’s natural oils (aka sebum), as the sebum breaks down, it produces a by-product called oleic acid. Lots of people are sensitive to oleic acid, so their scalp responds by becoming irritated and inflamed.
This inflammation causes the scalp to become red and itchy, leading the body to signal to the brain to shed skin cells at a faster rate to deal with it. Other factors such as stress, hormones and diet can also exacerbate it.
Oleic acid is a fatty acid, which is an odourless and colourless (to pale yellow) oil. This excess oil explains why dandruff flakes are usually oily, slightly sticky and yellowish in colour.