corrosion

Always test the dye on your arm to make sure you won't have an allergic reaction every time before you put it on your head. That way you can avoid this in the future.

As for now, wash your hair, and if you have any open wounds or your skin starts weeping, go to a doctor.

Don't leave dye on longer than you should. If the dye says you can leave it on 45 minutes, that means that after 45 minutes, the chemicals will be finished with what they can do to your hair, and longer isn't going to make a difference.

Be aware that if you're allergic to hair dye, you have to always mention that to your doctors and dentists, in case the anesthetics they may use on you have any similarity to the things in hair dye (which is possible).

It sounds like an allergic reaction or chemical sensitivity. Try putting aloe vera gel on it.

I think corrosion can only happen to metal. When you say there is "yellow stuff" there, what do you mean? Have you rinsed your hair really well to remove any product which may remain? Is your scalp irritated? Maybe it's just slightly stained from the colour you used. Did you use something with a gold or yellow base? If it's just stained, it will go away after you've shampooed a few times. If your scalp is actually burned or irritated, you can use shea butter or aloe vera to soothe it and speed up healing.

Juliana