Urine specimens from the eight individuals included in our study, who had used color lotion (natural black), were evaluated for mutagens by using the liver microsome activation method described by Durston and Ames.1 Urine specimens that were collected prior to the use of the hair colorant were tested also. Neither the control nor the experimental urine showed mutagenic activity. In addition, urine specimens from 75 regular users of hair-coloring products have been evaluated by the same technique. All evaluations were negative.
Yare RS, Garcia M. Percutaneous Penetration Following Use of Hair Dyes-Reply. Arch Dermatol. 1977;113(11):1610. doi:10.1001/archderm.1977.01640110130030