Objectives : To evaluate the DNA damage by hair dyeing in human lymphocytes Methods : Comet assays were carried out to evaluate the DNA damage in lymphocytes by hair dyeing. Twenty subjects were selected from women volunteers whose age ranged from 55 to 67 year old. All subjects had no smoking history. Blood samples were collected before and 6 hours after hair dyeing. DNA damage was evaluated by means of the tail moments, which were quantified by a KOMET 4.0 image analysis system. Results : The tail moments before hair dyeing showed no significant differences among subjects except for the high frequency group. The mean values of the tail moments in subjects with low and high frequencies of hair dyeing were 1.39 and 1.77, respectively (p<0.05). The tail moments after hair dyeing increased significantly, The mean values of tail moments in subjects before and after hair dyeing were 1.45 and 1.79, respectively (p<0.01). However, the difference levels of DNA damage in lymphocytes before and after hair dyeing were found to be slightly lower in both the dietary supplement taking group and high frequency group. Conclusions : The high frequency group appears to have a higher level of DNA damage than the low frequency group before hair dyeing. DNA damage in lymphocytes was found to be significantly higher in the volunteers after hair dyeing. In this study, the related factors such as high frequency and taking dietary supplements appeard to reduce DNA damage in lymphocytes after hair dyeing.