Quantitative studies were carried out into the fundamental measurements on human hair growth by the method using the optical microscope and image analysis, which was already developed.
The hair growth was studied with this method as to the regional differences between frontal, vertical, occipital and temporal regions using 14 healthy male subjects. The study revealed that the temporal hairs had the fastest growth rate, followed by the occipital, vertical and frontal hairs in descending order, and the ratios of resting or slow growing hair (hairs with a growth rate of 0.2mm/day or less) were quite reverse order in contrast with the growth rate. Then, age-related changes of hair growth were examined using 28 male subjects. It was learned that a decrease in the hair growth rate, terminal hair density, hair diameter and an increase in the ratios of resting or slow growing hair were significant with aging. This was remarkable in the vertical region. In addition, in the vertical region positive correlation was noted between the hair growth rate and the number of terminal hairs, whereas negative correlation was observed between the hair growth rate and the number of vellus hair.
Further, the hair growth was investigated using healthy and alopecia subjects. It was found that in the vertical region the hair growth rate was lower by 50% and the ratio of resting or slow growing hair was about 3 fold higher in the alopecia subjects than in the healthy subjects.
Finally, the effects of hair tonics on hair growth of alopecia subjects was studied by evaluating the hair growth before and after use of the test tonic or the control tonic for 6 months. The growth rate increased and the ratio of resting or slow growing hair decreased in the test tonic group. But, the former decreased and the latter increased in the control tonic group.
