The bacteria on your scalp could be to blame for your bad dandruff, scientists have discovered. Researchers in China found an imbalance between two specific kinds of bacteria led to more severe dandruff – a find that could lead to new ways of treating the condition.

Dandruff is a skin condition that causes flakes of dead skin to appear on the scalp. This can cause the scalp to become dry and itchy. Around half of all people will experience dandruff at some point in their lives, mainly affecting people in their early 20s. Researchers say the cause of the condition has been studied for decades, with fungi the most popular culprit. Yet no definitive answer has been widely accepted.

Scientists from Shanghai Jiao Tong University investigated the link between micro-organisms on the scalp, and the amount of dandruff. Specifically, they studied the two most abundant bacteria on the scalp: Propionibacterium and Staphylococcus.

The researchers tested the scalps of 59 individuals, collecting a total of 177 dandruff samples in the process (three from each participant). All of the volunteers had dandruff in varying quantities, and they washed their hair 48 hours in advance of the sample collections.

The results, published in Scientific Reports, show the severity of dandruff is linked to the ratio of the two bacteria species on the scalp. In the most extreme cases of dandruff, Staphylococcus was more prevalent than Propionibacterium. In participants with less dandruff, the amount of each bacteria was more equal.

The researchers say that "the balance between Propionibacterium and Staphylococcus might be important to the severity of dandruff." They suggest that adjusting the balance of the two bacteria by reducing the amount of Staphylococcus and increasing the level of Propionibacterium on the scalp could help control the condition.