How long should I wait to know that that hair dye won't irritate my skin?

I want to dye my hair green. But the directions say that I should test it out on a patch of skin to make sure it won%26#039;t irritate my skin, but it doesn%26#039;t say how long I should wait. Does anybody know?|||i dont even think you have to do that, i never did|||Put a bit of the dye behind your ear, and leave it there for 48 hours.





If it irritates your skin, don%26#039;t use the dye.





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