Sore itchy scalp after dyeing

Take an over the counter anti-histamine (allergy pill). You can also apply a hydrocortisone lotion to the scalp, in the US there is a product called Scalpicin. You may also want to see a doctor, it sounds like you have chemical burns which should be treated properly to avoid infection and scaring (which can cause bald spots)

You must likely suffered an allergic reaction to PPD. This is a common and VERY SERIOUS allergy, not to fearmonger but it can be deadly. You must have a patch test done before dying your hair again. If you do have a PPD allergy it is wise to never come in contact with PPD again, each time you do the reaction gets more severe. PPD is in most hair dyes unfortunately and darker shades contain more of it. Semi/direct dyes like the ones sold at beeunique are safe for those with PPD allergies (but you should still patch test any dye before use).

Thank you.  The only thing I've got to hand tonight is aloe vera gel - not sure if I've enough to get through the mountain of hair I have.

I've got an appointment to see the nurse at my doctor's surgery in the morning.

I suppose I need to ask the hairdresser what brand dye she used as well.  It's so hot and itchy though.  It's hell - and I'm terrified my hair falls out!