What can result from failing to conduct a patch test before applying hair dye?

Failing to conduct a patch test before applying hair dye can lead to severe allergic reactions. A patch test involves applying a small amount of the hair dye on a small area of the skin, typically behind the ear or on the inner elbow, to check for any adverse reactions. This is important because hair dyes contain chemicals that can trigger allergies in some individuals. Reactions can range from mild irritation to severe conditions such as rashes, swelling, and difficulty breathing. Conducting a patch test helps ensure the safety of the client and minimizes the risk of these potentially serious allergic reactions.

The other choices do not relate to the consequences of skipping a patch test. For example, longer-lasting color and less risk of color fade pertain to the dye itself rather than the safety measures taken before application, while improved hair texture is unrelated to the skin's reaction to dye ingredients. Therefore, the most critical outcome of neglecting to conduct a patch test is the potential for a severe allergic reaction.