Every Time I Have My Hair Dyed, My Stylist Fails

Every time I have my hair dyed, my stylist fails to fully rinse my neckline. Each time this happens I get a big on my neckline within 12-24 hours. Not bumps...lumps about 1 inch pertrusion. Then after additional 24 -48
Hours, and showering off neckline dye, the lumps fern we'll go away. What is this??