Table 2. Detailed Characteristics of Major Hair Dye Ingredients^a.

compound	yearb	maximum allowable concentration (%)	LD50 (mg/kg)c	toxicity	carcinogenicity	ref
N,N-bis(hydroxyethyl)-p-phenylenediamine 5 sulfate salt	1984	≤5	264	reduced body weight; darkened thyroid glands; decreased serum iron concentration; delayed hypersensitivity; allergic contact dermatitis	no evidence	(10)
N-phenyl-p-phenylenediamine 4, N-phenyl-p-phenylenediamine HCl	1993	≤1.7	464–1000	reduced body weight; degenerated seminiferous tubules; skeletal malformations; skin irritation	no evidence	(11)
hydroxypropyl bis(N-hydroxyethyl-p-phenylenediamine) 6 HCl	NA	≤0.4	2186	reduced body weight, mean serum glucose and total protein levels; reproductive and developmental toxicity	no evidence	(12)
4-methoxy-m-phenylenediamine 8, 4-methoxy-m-phenylenediamine sulfate salt, 4-methoxy-m-phenylenediamine HCl	1978	NA	400–500	skin irritation; mutagenicity	animal carcinogenicity	(13)
2-chloro-p-phenylenediamine 7, 2-chloro-p-phenylenediamine sulfate salt	1984	≤1.0	NA	skin irritation; reduced body weight; ocular irritation	no evidence	(14)
2-methyl-5-hydroxyethylaminophenol 10	NA	≤5	5700	skin irritation; mutagenicity; allergic contact dermatitis	no evidence	(15)
p-methylaminophenol 9 sulfate salt	NA	≤1	NA	increased rate of formation of methemoglobin; skin irritation	no evidence	(16)
2,4-diaminophenol 11, 2,4-diaminophenol dihydrochloride salt	1993	≤0.2	240	skin irritation; severe ocular irritation; mutagenicity	no evidence	(17)
hydroquinone 12	1981	≤1	627–743	nephrotoxicity; cytotoxicity; skin irritation; skin sensitization; skin depigmentation; mutagenicity	animal carcinogenicity	(18, 19)
t-butyl hydroquinone 13	1981	≤0.1	480–800	reduced body weights; mutagenicity	no evidence	(20)
toluene-2,5-diamine 14, toluene-2,5-diamine sulfate salt	1984	≤4	98–102	skin irritation; skin sensitization; ocular irritation; reproductive toxicity; skeletal malformation	no evidence	(21−23)
toluene-3,4-diamine 15	1984	NA	NA	duodenal lesions; genotoxicity; skin sensitization	no evidence	(21, 22)
Disperse Blue 7 16	2002	NA	NA	mutagenicity	no evidence	(24)
Disperse Violet 1 17	1988	≤1	NA	ocular irritation	no evidence	(25)
Disperse Yellow 3 18	1992	NA	NA	nephrotoxicity; chromosomal aberrations; allergic contact dermatitis	animal carcinogenicity	(26)
Acid Violet 43 19	1984	≤1	NA	no significant toxicity	no evidence	(27)
Basic Blue 99 20	1992	≤2	>2000	skin irritation	no evidence	(28)
HC Blue no. 2 21	1993	≤1.7	1250–5000	mutagenicity	no evidence	(29)
HC Yellow no. 5 22	2002	≤1.6	555.56	skin irritation	no evidence	(30)
HC Red no. 7 23	2005	≤1	NA	skin sensitization; mutagenicity	no evidence	(31)

^aFor chemical structures, refer to Figure 1.

^bThe first yearly report by the Food and Drug Administration.

^cThe oral LD₅₀ in rats of aqueous solutions. Abbreviations: LD₅₀, median lethal dose; NA, not assessed.