What should be applied to protect a client's skin during a chemical treatment?

Using a base cream to protect a client's skin during a chemical treatment is essential for several reasons. A base cream acts as a barrier between the skin and the chemicals involved in the treatment, reducing the likelihood of irritation or adverse reactions. This protective layer helps to ensure that the chemicals do not come into direct contact with the skin, which can prevent burns or allergic reactions.

Additionally, base creams often have specific properties that can enhance skin protection, such as being rich in emollients, which can soothe the skin and help maintain moisture balance. This is particularly important during chemical processes that may be harsh or drying.

The other options, while they may serve different purposes, do not provide the same level of protection. Water can dilute chemicals but does not effectively protect the skin. Shampoo is formulated for cleansing hair and does not have protective properties for the skin in the context of chemical treatments. Moisturizers, while beneficial for hydration, do not create a sufficient barrier to guard against the chemicals used in treatments. Therefore, applying a base cream is the best choice for ensuring client safety and comfort during chemical applications.