Before using hair dye at home or having your hair colored at a salon, you or the colorist should do a patch test to make sure you won't have a bad reaction. Place a small amount of the dye on the inside of your elbow or behind your ear, and leave it there for two days. If you haven't had a reaction in two days, the dye should be safe to use on your head.
If you're using hair dye at home, be sure to read and follow the package instructions carefully. Never use hair dyes on your eyelashes or eyebrows.
If you have any concerns about adverse reaction to hair coloring products, talk with your doctor or dermatologist.