Hair dyes and aplastic anemia.

Reports linking the use of hair dyes with bone marrow suppression and aplastic anemia have appeared sporadically over the past 45 years. For the most part these clinical cases are difficult to evaluate but appear to rely heavily for support on a single report in 1935. The infrequency of these reports and the wide-spread use of hair color products argue strongly against a primary toxic action on bone marrow in humans. The results of studies in three species of animals support this conclusion, giving no indication that chronic exposure to hair dyes causes adverse effects on hematopoiesis. Although it cannot be dismissed as a possibility, invoking idiosyncrasy seems on equally shaky grounds since any rational basis for continued association of a substance with individual sensitivity should find increasing numbers of cases with increasing population exposure. Clearly this has not been the case.