Final answer:
Chemical peels should be avoided over the thin and delicate skin of elderly clients as it may cause injury.
Step-by-step explanation:
The technique that is best avoided over the thin and delicate skin of elderly clients as the skin may be injured is chemical peels. Chemical peels involve the application of a chemical solution to the skin, which exfoliates the top layers of the skin to reveal a smoother and more youthful complexion. However, this technique can be too harsh for thin and delicate elderly skin, which may result in irritation, redness, and even burns.