After using the 2-steps for dyeing hair, which is using henna first, and then follow by indigo immediately, I have got headache and it last for more an hour. This don't happen if i just the 2 powders together and put on the hair for about 2 hours. Also the indigo only lies in the hair for about 30-45 minutes. The headache not only happens on me but alo on my friend.