Which of the following is NOT a reason for dandruff?

Excessive hair brushing is not a recognized cause of dandruff. Dandruff is primarily associated with factors affecting the scalp's condition and health. While over-brushing hair can lead to temporary issues such as irritation or damage to the hair and scalp, it does not directly cause the flaking characteristic of dandruff.

On the other hand, an oily scalp can lead to a buildup of sebum, which may create an environment conducive to the overgrowth of Malassezia, a type of fungus linked to dandruff. A dry scalp can also result in flaking skin, contributing to the appearance of dandruff. The overgrowth of fungal organisms, specifically Malassezia, is a well-documented factor in the development of dandruff, as it can lead to inflammation and cell turnover, resulting in visible flakes.