Well, you should definitely avoid future hair dye-ing if you are subject to allergic reactions. For now, you might try applying ice to the scalp to see if that will relieve the itching, or applying some type of anti-itch lotion like Calamine. It might also help to take an over the counter antihistamine like Benadryl, but I can't advise whether any medication is really safe for you over the Internet, as I know nothing about you or your medical condition.
Discuss your symptoms with your doctor and/or pharmacist to get more specific recommendations.
Best,
Kathi
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