What problems can occur when colouring hair?

When coloring hair, several problems can arise, including allergic reactions to the dye, which may cause irritation or skin rashes. The hair can also become damaged or over-processed, leading to dryness, brittleness, and breakage. Additionally, uneven color results or unwanted tones may occur if the dye is not applied correctly or if the hair's condition affects color absorption. Finally, there can be issues with fading or color maintenance, requiring frequent touch-ups and special care.