- Double recessive reds have thick hair for a lower density per mm²
- A mutation locus encodes eumelanin which having unique aromatic properties
- Children and young adults are sensitive to indelicate treatments on the scalp such as ammoniacal discolorations
- Increasing incidence of melanoma and endometriosis
- In the XVth century, justice delivered to the secular arm, the fate of heretics who had to free their soul from the particular color of their red hair