Ethnic characteristics of eyelashes: a comparative analysis in Asian and Caucasian females

BACKGROUND: Despite similar biochemical composition of human hair between races, physico-morphological characteristics are not identical in different ethnic groups. Eyelashes have been investigated far less than scalp hair, and the information available is insufficient. OBJECTIVES: To obtain basic information about eyelashes and to clarify differences between female eyelashes in Asians and Caucasians. METHODS: Twenty Asian and 10 white Caucasian female volunteers aged between 20 and 29 years were admitted to the study. Lateral digital photographs of upper eyelashes were taken and curl-up and lift-up angles of upper eyelashes were measured from lateral views. Images of upper eyelashes were also taken using the phototrichogram technique and total numbers, lengths and thicknesses of upper eyelashes were obtained (a total of 4661 eyelashes; 2946 for Asian, 1715 for Caucasian). The central portion of the eyelashes or whole eyelashes were clipped and images were taken immediately and 7 days later to obtain the growth rate and anagen ratio of upper eyelashes. Numbers and thickness of eyelash cuticular layers were obtained by electron microscopy. RESULTS: Compared with Caucasians, Asian eyelashes revealed lower lift-up and curl-up angles, fewer numbers and a thicker transverse diameter. However, no statistical difference was observed in length or growth rate. Duration of anagen was estimated at about 2 months. The eyelash anagen ratio obtained from five Asians was 17.8 +/- 3.3%. By electron microscopy, the number of cuticular layers in transverse section was greater in Asian (8.0 +/- 1.2) than Caucasian females (6.5 +/- 1.1), but no statistical difference was found in single cuticle layer thickness between the two groups. Moreover, eyelash characteristics were not influenced by eye makeup in either race. CONCLUSIONS: Our results on eyelash morphology and growth characteristics demonstrated significant ethnic differences in Asian and Caucasian females that could provide basic information for future investigations