Table 3.

Summary results of cell viability and interleukin (IL)‐18 secretion for inks, additive, and irritant

	Concentration (%)	Cell viability  ±  SEM (%)	EC50 (%)	IL‐18 SI  ±  SEM	N
Tattoo ink
Eternal Ink Light Red	0.01	57 ± 16	0.04	11 ± 7.6	5
	0.1	33 ± 13		31 ± 17
	1	12 ± 3.0		88 ± 45
	10	6.4 ± 2.2		50 ± 13
Intenze Gold Label Bright Red	0.01	110 ± 6.1	6.3	1.2 ± 0.48	5
	0.1	103 ± 8.5		0.9 ± 0.15
	1	80 ± 11		4.1 ± 1.3
	10	6.4 ± 1.6		4.1 ± 1.4
Intenze Sculpting Black	0.01	78 ± 7.7	0.09	1.9 ± 0.37	5
	0.1	47 ± 10		29 ± 14
	1	15 ± 4.0		41 ± 16
	10	5.8 ± 1.0		62 ± 15
Carbon Black No. 13 Blackout	0.01	90 ± 5.0	12	1.4 ± 0.23	4
	0.1	99 ± 4.6		1.5 ± 0.23
	1	86 ± 9.4		1.5 ± 0.28
	10	57 ± 14		1.3 ± 0.56
Intenze True Black	0.01	85 ± 11	NR	1.1 ± 0.19	4
	0.1	88 ± 13		0.8 ± 0.18
	1	94 ± 13		1.4 ± 0.50
	10	79 ± 7.6		0.7 ± 0.28
Additive
Hamamelis virginiana extract	0.01	105 ± 10	100	1.6 ± 0.35	4
	0.1	82 ± 11		2.5 ± 0.39
	1	80 ± 13		2.8 ± 1.12
	10	79 ± 3.8		1.2 ± 0.25
Control irritant
Lactic acid	0.03	84 ± 7.4	0.05	1.4 ± 0.24	3
	0.06	11 ± 1.9		8.3 ± 3.9
	0.1	9 ± 1.0		0.1 ± 0.02
	0.3	12 ± 2.7		0.0 ± 0.01

Abbreviations: N, number of experiments; NR, not reached; SEM, standard error of the mean; SI, stimulation index.

Eternal Ink Light Red and Carbon Black No. 13 Blackout exposure conditions are expressed relative to the vehicle isopropanol (1% wt/wt); all other exposure conditions are expressed relative to the vehicle glycerol (1% wt/wt). IL‐18 SIs of ≥10 are indicated in bold, and are indicative of the substance being a skin sensitizer, as this value is higher than that obtained for lactic acid.