What should a barber do if a client indicates an allergy to a product?

If a client indicates an allergy to a product, the most appropriate course of action is to avoid using that product and seek an alternative. This approach prioritizes the client's safety and well-being. Allergic reactions can range from mild irritation to severe anaphylactic responses, and the consequences of exposure to an allergen can be serious.

By opting for an alternative product, the barber demonstrates professionalism and care for the client's health needs. It is crucial for barbers to be aware of clients' allergies to ensure that all services provided are safe and tailored to individual client needs. The other options might not fully protect the client from potential harm; for example, using the product carefully or providing a patch test may not eliminate the risk of an allergic reaction. Informing the client about the ingredients is important, but it doesn't address the immediate need for a safe solution. Therefore, seeking an alternative product is the most responsible action in this scenario.