The Question on the Potential Cancerous Effects of Hair Dyes: The Monitoring of the Oxidative Stress Induced by the Hair Dyes with the Dosage of the Salivary Free Radicals

BACKGROUND: Many studies indicate the difficulty on assessing the possible carcinogenic effects of hair dyes, for their high time of the latence. OBJECTIVES: Our objective is to determine their prognostic index, by monitoring the oxidative stress, produced exposed to hair dyes, in hairdressers, and in consumers, by measuring the concentration of salivary malondialdehyde. MATERIALS AND METHODS: Saliva samples are provided by the hairdressers, working in private (NP) or shopping center (CC), by users of hair dyes, for at least 10 years, and by a control group. The values of malondialdehyde are determined using the thiobarbituric acid method. The results are statistically analyzed by Kruskal–Wallis and Mann–Whitney test. RESULTS: Comparing the three groups with tests for K-independent Kruskal–Wallis samples (dyed vs. control vs. dyed at least 10 years), there is a significant difference for the amount of MDA (P < 0.001). Proceeding for the median MDA in the subgroups by testing for two independent U-samples of Mann–Whitney: control versus dyed, P < 0.001; control versus CC, P = 0.013; control versus NP, P < 0.001; control versus 10 years, P = 0.111; CC versus NP, P = 0.001; CC versus 10 years, P = 0.462; and NP versus 10 years, P < 0.001. DISCUSSION: In hairdressers, the increase of the salivary MDA versus control group is statistically significant (P ≤ 0.05), with an accentuation in small workplace, for age, probably for a more direct exposure to dyes' gas. Another statistically significant increase of salivary MDA is for the consumers versus control group, also function of the increasing age. CONCLUSIONS: The results of this study show a significant increase of oxidative stress in the hairdressers. This factor involves a potential carcinogenic risk, especially for the bladder, difficult to assess in the short term.