I used a brown hair dye on my head which probably had henna in it which I am allergic too but I didn't know it was in hair dyes. After I dyed it a rash appeared as well as my head swelling up but not my face. It went away and the swelling went down after I got a cream from the doctor, a month later bald patches appeared at the back of my head. After a while the hair stopped falling out but now four months later the bald patches are still there I have seen the doctor a few times but he just keeps saying its fine and it will grow back. I have lost a lot of self esteem and I am constantly wearing a hat to cover my head and I'm really beginning to worry that my hair isn't going to grow back has anybody suffered from this or know anything about this that they could give me advice about please?

There are henna preparations that are used for coloring hair, but they definitely do not put henna in hair dyes. I suspect that you've become allergic to the p-phenylenediamine dye in the haircolor. This is a well-known allergen. I suggest you talk to a dermatologist or possibly to an allergist.