I have an itchy scalp and a large red itchy patch on my forehead. I also have swollen lymph nodes around my ear. I got my hair done last Wednesday.

Dermatitis. If ALL the symptoms are on SAME side of your head and don't cross the midline then I'm worried about shingles which can later become painful. Starting treatment right away is critical A chemical allergic reaction is also possible especially if your hair was dyed and should have it looked at.