Regular use of hair dyes and risk of lymphoma in Spain

Background The use of hair dyes has been inconsistently associated with an increased risk of lymphomas. We explore hair dye use and lymphoma risk in a case-control study in Spain. Methods We studied 574 incident lymphoma cases and 616 hospital controls in a multicentric study in Spain. Information on hair dye use was obtained through a personal interview together with information on other known or putative risk factors for lymphoma. Unconditional logistic regression analysis was used to estimate odds ratio (OR) and 95% confidence intervals (95% CI). All ORs were adjusted for pathology center, sex, age, and house ownership. Results Ever use of hair dyes was associated with a non-significant 20% increased risk of lymphoma (OR = 1.2, 95% CI 0.9-1.7) with a slightly higher risk observed for those using permanent hair dyes (OR = 1.3, 95% CI 0.9-1.9). No association was observed with duration of use or lifetime doses of hair dyes. Among all lymphomas categories, only chronic lymphocytic leukaemia (CLL) was significantly associated with the use of hair dyes (OR = 2.3, 95% CI 1.1-4.7). The risk of CLL increased with lifetime doses received. Conclusions Ever use of hair dye products is unlikely to substantially modify the risk of lymphoma. The observed association with CLL needs to be replicated.