Yes, you absolutely should. However, apply Protein Spray throughout the previously treated areas then wait 30 minutes before proceeding to the regrowth application with bleach. The reason I suggest waiting 30 minutes, is in instances where bleach regrowth is being undertaken, you do not want the hair too damp. You need a level of dryness as it prevents the bleach slipping onto previously lightened areas. Therefore, applying the Protein Spray throughout, combing and then allowing the protein to dry off a little will enable good precision (without slipping) when the bleach is applied to the dark regrowth areas.