2010 TRI/PRINCETON CONFERENCE 197 Piedmont hair the Trp signal increases as a result of bleaching. It is important to point out that Piedmont hair loses almost all of its pigmentation upon bleaching, especially its yellow hue, which more than likely comes from kynurenine (11,12,14). HAIR STRAIGHTENING Commonly employed by individuals whose hair can be characterized as very tightly curled (e.g. African type hair) or frizzy, hair straightening formulations (chemical relaxers) rely on the activity of strongly basic formulations which result in chemical and morphological changes in the hair shaft. Traditionally, NaOH based (lye) relaxers were employed to carry out such a task, resulting in a great deal of damage to the fi ber including cleavage of disul- fi de bonds, changes in protein conformation (α-helix to β-sheet transitions), and the forma- tion of lanthionine crosslinks. More recently, lower pH chemical relaxers have been introduced into the market place however, they still damage the fi ber. In the present study, we examine the effects of hair straightening with a lye relaxer on hair fl uorescence. The peak intensities and ratios for chemically relaxed hair are provided in Table II. As a result of relaxer treatment, Trp fl uorescence decreases for both dark brown and Piedmont hair (compared to untreated readings in Table I). In contrast, the signal for IKyn is essen- tially the same as for untreated hair in both (dark brown and Piedmont) cases. Although Trp degradation to kynurenines may occur—which would lead one to expect an increase in IKyn—the kynurenines themselves may be degraded by the relaxer treatment. In the case of the peak at the highest excitation wavelength employed, I509, relaxer treatment results in a large decrease in peak intensity for Piedmont hair and no change for dark brown hair. This effect may be more pronounced for Piedmont hair since its fl uorescence in this region is much more discernible. The peak ratios are also provided in Table II, which correspond with the peak intensity observations. THERMAL DEGRADATION OF HAIR Frequently, hair is exposed to thermal treatments to provide desired hair set or style. In previous studies, we found that hair experiences surface (cuticular) and internal (cortical) damage as a result of thermal treatment (7). Hair also undergoes color changes upon ex- posure to heat. This is clearly evident in the photograph of Piedmont hair shown in Figure 4, Table I Peak Intensity Values and Pertinent Peak Ratios for Dark Brown and Piedmont Hair in the Virgin and Bleached States ITrp IKyn I509 ITrp/IKyn I509/IKyn Dark brown 27,300 ± 1,838 104,650 ± 7566 26,250 ± 212 0.261 ± 0.001 0.252 ± 0.020 Dark brown- bleached 31,000 ± 707 222,000 ± 22,627 137,500 ± 3,536 0.141 ± 0.017 0.622 ± 0.047 Piedmont 47,400 ± 2121 2,135,000 ± 134,350 1,540,000 ± 169,705 0.022 ± 0.000 0.720 ± 0.034 Piedmont- bleached 85,150 ± 2899 3,205,000 ± 49,497 1,585,000 ± 106,066 0.026 ± 0.000 0.494 ± 0.025

JOURNAL OF COSMETIC SCIENCE 198 where one can visually observe the region of the tress where hot iron treatment was ad- ministered, resulting in the formation of a dark yellow hue. In the case dark brown hair, we do not observe a visually signifi cant color change, probably because it is masked by the absorption of melanin. Thermal treatment was administered for 1 min. of continuous treatment. For this particular hot iron application, such a length of treatment might be considered extensive. However, this time-scale was meant to be representative of cumu- lative treatments (i.e. a series of short treatment protocols) providing an overall equiva- lent treatment time to the continous treatment. In fact, previous studies show that cumulative treatment is actually more damaging than continuous treatment (7). Data extracted from the excitation-emission matrices for thermally treated Piedmont and dark brown hair are provided in Table III. For dark brown hair, we observe a decrease in the residual Trp levels while the IKyn and I509 bands are statistically similar when compar- ing the thermally exposed region of the tress with the unexposed portion. The calculated peak ratios reveal the same information. In Piedmont hair, thermal exposure results in Trp loss, degradation of kynurenines, and an increase in the intensity at I509. As expected, the ratio, ITrp/IKyn, decreases in thermally exposed hair as compared to the unexposed re- gion of the tress. In contrast, there is an increase in I509/IKyn in thermally exposed Piedmont hair. We suspect that the formation of yellow coloration in thermally exposed hair is re- sponsible for the observed increase in this ratio. Table II Peak Intensity Values and Pertinent Peak Ratios for Dark Brown and Piedmont Hair Exposed to Chemical Relaxer Treatment ITrp IKyn I509 ITrp/IKyn I509/IKyn Dark brown- relaxer 19,150 ± 636 108,000 ± 2,828 26,650 ± 1061 0.177 ± 0.001 0.247 ± 0.003 Piedmont- relaxer 26,150 ± 1,485 2,155,000 ± 35,355 728,700 ± 28,284 0.012 ± 0.000 0.672 ± 0.002 Figure 4. Photographs of thermally exposed (A) Piedmont and (B) dark brown hair.