Final answer:
It is crucial to replace cotton around the hairline during a perm service when it becomes saturated with perm solution to prevent skin irritation or burns.
Step-by-step explanation:
During a perm service, it is important to replace cotton around the hairline whenever it becomes saturated with the perm solution.
The cotton is there to protect the skin from the chemicals by absorbing any excess solution that may drip down.
As perms involve the application of chemicals to change the hair structure, safety is paramount to prevent skin irritation or burns. Cotton should be checked regularly and replaced as needed to ensure the client's comfort and protection.