Iowa Cosmetology Practice Exam 2026 - Free Cosmetology Practice Questions and Study Guide

A patch test is performed before a color service primarily to check for allergic reactions to products. This step is crucial because it helps to identify whether the client has a sensitivity or allergy to any of the chemicals present in the hair dye or color product. By applying a small amount of the color formulation on a discreet area of the client's skin, typically behind the ear or on the inner elbow, the cosmetologist can observe any adverse reactions, such as redness, swelling, or irritation, within a specified timeframe, usually 24 to 48 hours.

This practice enhances client safety by preventing potential allergic reactions during the full application of the color service. Ensuring that customers are not allergic to the products used minimizes the risk of discomfort or serious allergic responses, which could lead to severe reactions or complications during or after the hair coloring process.

The other options focus on different aspects of the hair coloring process. Determining the desired shade, assessing hair texture, and evaluating the effectiveness of clarifying treatments are all valid considerations in cosmetology but do not specifically address the need for ensuring safety through allergy testing prior to any chemical service.