What is a common sign of an allergic reaction to hair dye?

Itching and redness on the scalp are common signs of an allergic reaction to hair dye. When someone is allergic to the chemicals found in hair dye, particularly an ingredient called para-phenylenediamine (PPD), the body's immune response can cause localized skin irritation. This can manifest as itching, redness, swelling, and sometimes even blisters. Recognizing these symptoms is crucial for anyone working in cosmetology, as they indicate that a client may have a sensitivity to a product that could cause further complications if used again.

Other options present different hair or scalp conditions that are not typically related to allergic reactions. Increased shine in hair, for instance, is a result of proper hair care and conditioning rather than an allergic response. Faster hair growth is biologically driven and usually unaffected by hair dye; it is influenced more by genetics and health rather than the application of hair color. Finally, hair becoming brittle can be caused by over-processing, lack of moisture, or certain health issues, but it does not specifically indicate an allergic reaction to hair dye. Understanding these distinctions helps to ensure safe practices in a salon environment.