What is a potential consequence of overlapping lightener during a retouch service?

During a retouch service, overlapping lightener can lead to damage in the hair, specifically resulting in breakage. This occurs because the previously lightened hair has already been chemically altered, making it more vulnerable to additional processing. When new lightener is applied over areas that have already been treated, the extra processing can weaken the hair structure, leading to dehydration and ultimately breaking.

Understanding the hair’s physiological response to chemicals is crucial in this context. Proper techniques involve only applying lightener to the new growth to prevent unnecessary overlapping. Maintaining hair integrity is essential for color treatment, and avoiding overlap helps preserve the hair’s strength.