Personal use of hair dyes--increased risk of non-Hodgkin's lymphoma in Thailand.

The use of hair dyes has been inconsistently associated with an increased risk of lymphomas. To further evaluate this possibility, we examined hair dye use and lymphoma risk in a case-control study in the Thai population. A total of 390 histologically confirmed incident non-Hodgkin's lymphoma (NHL) cases and 422 controls were included. Information on hair dye use was obtained through a personal interview together with information on other known risk factors of lymphoma. Analysis was performed using logistic regression; odds ratios (ORs) estimates and 95% confidence intervals (CI) were calculated. Ever use of hair dyes was not associated with an increase risk of NHL both overall (OR=1.1, 95%CI 0.8-1.5) and in women (OR=1.4, 95%CI 0.9-2.3). However, NHL was significantly higher among persons who began using hair dyes before 1980 (OR=2.1, 95%CI 1.0-4.1). An increased risk was also observed among women who reported use of permanent hair dye product (OR=1.8, 95% CI 1.0-3.1). Analyses by NHL subtype showed an increased risk for diffuse large B-cell lymphoma among users of permanent hair dyes (OR=1.6, 95%CI 1.0-2.5) while follicular lymphoma was associated with the use of dark-colored dyes (OR=3.7, 95%CI 1.1-12.8). No association was observed with duration of use, nor total lifetime applications. These results indicate that personal hair dye use may play role in risks of NHL among person who used hair dyes before 1980.