Hair curl type, hair habits and scalp heath, part 1: Clinical studies

Background Very curly, textured hair is often associated with specific scalp conditions, such as traction alopecia and seborrheic dermatitis. However, to date, very few detailed clinical studies have been performed to correlate scalp conditions to curl type and hair habits. Methods Healthy female panelists, with hair not damaged by chemical treatment , were recruited in both the US and South Africa (SA) based on their natural curl type: wavy (Walker Type 2), curly (Walker Type 3) or kinky (Walker Type 4). Both scalp and hair assessments were performed at visit 1 (baseline) and at visit 2, 1 week afterwards. Between the visits, panelists were asked to wash their hair four times with a standard shampoo and conditioner selected and provided by the authors. Results A significant proportion of panelists with Type 4 hair washed their hair less frequently than panelists with the other hair types and were more inclined to use hair styling techniques (braiding, extension, knots, etc.), which induce tension on the scalp. They also self‐perceived having drier and less oily scalps than panelists with the other hair types. Dermatologists' assessments showed the incidence of seborrheic dermatitis was higher in Hair Type 4 in the US. Dermatologists observed the highest levels of traction alopecia in Hair Type 4 in both countries. Scalp image analysis showed that visible scalp scaling was more common in Type 4 hair versus other hair types in both the US and SA. Washing the hair every 2 days between the two visits improved self‐perceived scalp cleanliness and scalp condition across all curl types in both countries. Conclusions Our results confirm that more frequent use of specific styling practices in Type 4 hair is linked to higher levels of traction alopecia. Results also suggest that lower wash frequencies observed mainly with Type 4 hair were associated with a higher degree of scalp irritation and scaling and that washing hair more frequently has the potential to improve scalp health. Our data also suggest that scalp image analysis is a more consistent way of measuring scalp colour and scaling.