Dyed my hair got an allergic reaction and bumps have spread to my neck?

Contact allergy. U will probably want to see a dermatologist or allergist for patch testing. It may identify what chemical in the hair dye that u r allergic to. This way u can avoid other products w the same chemical.
Try to wash it out. Wash out as best you can...Then take antihistamines(benadryl, allegra, (fexofenadine) zyrtec--read the labels) and try 1% cortisone cream..If it gets worse see your dr. You might need oral steroids .