I dyed my hair and it was very painful. The chemicals got into the open sores and I had to wash it out right away because of the pain.
Ask your doctor to be absolutely sure. But, in my opinion ; if you don't know, then CHOOSE the safer one. Which means don't DO IT. --Until, of course, you get professional advice. :]
Seborrheic Dermatitis is an inflammation of the scalp that causes flakes. This disease can be very embarrasing as well as cause a lot of pain. Most chemical products are harmful for Seborrheic Dermatitis. Normally Chemical dyes contain hydrogen peroxide which can alleviate your problem even further. So dying the hair must be avoided during this disease. If you still want to dye your hair use a natural dye like Henna.