Which practice during retouching has the potential to cause hair damage by overlapping lightener?

• A. Not Overlapping the Re-Growth Area
• B. Extending Processing Time Beyond Recommended
• C. Overlapping Lightener Onto Previously Lightened Hair
• D. Using a Lower Volume Developer

Answer: (C)

Overlapping lightener onto previously lightened hair causes the most risk because the strands in those areas are already weakened from the first lifting. When you reapply lightener to the same zone, you pile on more peroxide and pigment, pushing the hair beyond its limits. This extra processing opens and damages the cuticle further, causes the cortex to lose protein, and makes the strand brittle and prone to breakage. In a retouch, the aim is to lighten only the new growth and avoid redoing the already lightened portions, so you don’t stack chemical stress on hair that’s already been stressed.

Not overlapping the re-growth area helps protect the lighter, more vulnerable mid-lengths and ends. Extending processing time beyond what's recommended increases overall chemical exposure and damage, but the issue there isn’t overlap with previously lightened hair. Using a lower volume developer reduces lift and chemical intensity, which generally lowers the risk of damage and isn’t about overlapping hair on already-lightened sections.