What is a common cause of scalp irritation during chemical services?

Overlapping hair color onto previously dyed hair is a common cause of scalp irritation during chemical services because it can lead to excessive chemical exposure on already processed hair and the scalp. When hair dye is applied over existing color, it can cause the chemicals to penetrate deeper than intended. This not only puts more strain on the hair's structure but can also lead to chemical burns or irritation on the scalp, particularly if the overlapping occurs repeatedly or if the formulations used are particularly harsh.

Other options do not typically lead to scalp irritation in the same way. For instance, using too much conditioner generally relates to hair texture and manageability rather than direct irritation. Drying hair with high heat is more about potential damage to the hair shaft than the scalp itself. Similarly, while applying too much styling product can lead to buildup that may irritate the scalp over time, it does not compare to the immediate effect of overlapping hair color.