Hair Breakage 264 Afro hair at 60% RH upon repeated application of a 0.010 g/μm2 stress. Under the same stimuli, Caucasian hair at 90% relative humidity will break after approximately 750 cycles. In short, the tendency for breakage in Caucasian hair has been raised to a level approaching that of relaxed Afro hair. One may immediately think about the amount of hair manipulation that takes place in humid bathrooms, while also noting the constant high humidity conditions that occur in certain geographical regions for significant portions of the year. In Southeast Asia, for example, consumers describe a condition known as “hair fall,” which relates to the general loss of hair fibers from the head during everyday habits and practices. This occurrence is often attributed to the natural shedding cycle of hair, but the above results indicate how hair breakage may be a much larger contributor than previously thought. Also striking about Figure 9 is the parallel alignment of the various S-N plots, which apparently suggests the manner by which the cycles-to-fail depends on the stress is approximately constant. Of course, intersection with the x axis for any data set occurs at the Figure 9. S-N Curves for Caucasian hair at different RH