Star Pauley Perrette from NCIS went to the ER with a severe allergic reaction to hair dye. Her character Abby Sciuto, a forensic scientist, is known for her shiny black hair on the show. Pauley made posts on Twitter in reference to her experience, claiming her head was swollen like a melon!
Many people have never had an allergic reaction to hair color. Pauley, however had a severe reaction. Severe swelling of the head, that could have turned fatal in some cases. Luckily for this star everything worked out for the better. Some more milder reactions can be break outs that just itch to sometimes hives. Allergic reactions that are caused by hair dye sometimes do not develop right away and become an aquired allergy. Meaning you could be getting your hair colored for years like Pauley Parrette was before your affected.
If you have concern as to whether or not you will have an allergic reaction you have a patch test done. Apply a small amount of color on a cotton ball and dab it on the skin behind your ear. Leave it there for 24 hours. If you are going to have an allergic reaction it will occur during that time frame. If you don't have an allergic reaction then you're good to go. Sometimes the brand of color makes a difference too. Sometimes its not the color but some of the other ingredients that are in the color. So if you have a reaction to the patch test, try a couple of brands before giving up hope. If you don't want to do this yourself stylists will be gladly to assist you. If you do have a reaction sometimes you can still get colors foiled in, like highlights and lowlights, so that the color doesn't touch the scalp giving no allergic reaction.