Why should products be patch-tested or chosen carefully for clients with sensitive skin or allergies?

For clients with sensitive skin or known allergies, products should be selected carefully and, where appropriate, patch-tested, to avoid triggering an allergic or irritant reaction that could cause redness, itching, swelling, or worse. Knowing the client's sensitivities (gathered during consultation) and choosing suitable, gentle products protects the client. If a client reports allergies to certain ingredients, those products must be avoided. Recognizing the importance of allergy awareness and patch testing in skin services is part of the safety content on the exam.