Dandruff scalp microbiome exhibits flake severity and sex-related differences

Dandruff is a prevalent scalp condition characterized by flakiness and itchiness. Its severity can be assessed clinically based on the grade of flakes and coverage area of flakes adhering to the scalp. Dysbiosis of the scalp microbiome is a key factor associated with dandruff, as revealed by studies comparing healthy individuals with those with dandruff.

This study further investigated the interplay between microbiome alterations and dandruff severity, and whether these changes are consistent across different sexes.

Dandruff condition was assessed using the Total Weighted Head Score for Adherent Flakes (TWHS AF). Male and female participants with lower dandruff severity (TWHS AF = 32-40 inclusive) and higher dandruff severity (TWHS AF ≥ 44) were recruited following ethical clearance of the study and obtaining informed consent. Scalp bacterial composition was investigated by 16S rRNA amplicon sequencing. The absolute abundance of key scalp microbes was quantified by quantitative polymerase chain reaction.

Notable microbiome compositional differences were observed between scalps with lower and higher dandruff severity. More severe dandruff exhibited a significantly reduced abundance of Cutibacterium acnes and elevated levels of Staphylococcus capitis and Corynebacterium spp. The absolute numbers of Malassezia restricta significantly increased with increased dandruff severity, while M. globosa remained similar. Additionally, distinctive scalp microbial profiles were observed between female and male participants with dandruff, even with the same levels of severity. Interestingly, beta diversity analysis revealed that the microbiomes from male participants with less severe dandruff clustered closely with those of male and female participants with more severe dandruff. Similarly, microbiome metabolic pathway profiles indicated that metabolic alteration in male participants with less severe dandruff was more similar to male and female participants with more severe dandruff.

Our findings underscored significant severity-associated variations in microbial ecology. For the first time, we unveiled sex-related differences in microbiome profiles among individuals with dandruff, with male profiles resembling a severe dandruff dysbiosis state. These results highlight a progressive development of microbiome dysbiosis with dandruff severity and suggest potential mechanistic differences between male and female dandruff conditions, which may require different intervention strategies.