How do i get rid of a allergy rash on my neck that i got from hair dye?

okay well i have been allergic to hair dye for like a year now, and i decided to try it out after like a year of not dyeing my hair, and i got the rash all over my neck, head and ears. I managed to get rid of the rash on my head and ears but the rash on my neck just wont clear up, I have tried using antihistamines for 6 days and also antihistamine cream on the area for around 2 weeks and it wont move. The rash is dry and itchy so i also used some moisteriser