What Causes A Sensitive And Itchy Spot On The Scalp?

Good Afternoon I suffered from a bald patch at the center of my hair approximately four years ago.The hair grew back very thick but within the past two years the area has become very sensitive and itchy,as well as the hair texture at the bald patch area has changed.I have chemically relaxed hair.Thick hair not think generally at all,however the texture of hair where I got the bald patch has changed drastically and become very course,dry and brittle.The hair in that area breaks easily and becomes very tough to deal with.I currently take hair finity vitamins that is helping but I realise that my hair in that area is still breaking noticeably.Can you assist me ??