Normal skin replacement is about 28 days. Due to reasons such as insufficient sleep, stress, unhealthy diets and hormonal changes, the replacement cycle (keratinisation) is shortened. This shortening of the replacement cycle results in new skin cells being generated at a faster pace than the shedding of the dead skin cells on the scalp surface. Over time, the accumulation of the dead skin cells forms the dandruff that we see on your scalp.