What precautions should I take before using this permanent dye, especially with a sensitive scalp or damaged hair?

Permanent hair dyes contain oxidative agents (typically hydrogen peroxide) and alkalizing agents (ammonia or substitutes) that open the cuticle and develop color inside the hair shaft. This process is inherently stressful to both scalp and fiber. The manufacturer explicitly advises a sensitivity test 48 hours before each application — even if you've used this brand before — because allergies can develop at any time. Mix a tiny amount of color cream and developer, apply behind the ear or on the inner forearm, leave uncovered, and watch for redness, itching, burning, or swelling. If any reaction occurs, do not use the product. Beyond allergy risk, assess your hair's condition: if the ends snap easily when wet, feel mushy, or have significant split ends, the dye will likely worsen the damage and the color may take unevenly. In that case, trim first and treat with protein/moisture masks for a couple of weeks before coloring. If you've recently had a perm, relaxer, keratin smoothing treatment, or bleach, wait at least two weeks (preferably four) to let the hair's protein structure stabilize. For sensitive scalps, apply a barrier cream or petroleum jelly along the hairline and partings, and consider a lower-volume developer if the kit allows choice — though this specific product comes with a fixed developer strength calibrated for the 7.5 shade.