What type of information can help an esthetician avoid potential allergic reactions during treatment?

Understanding a client's past allergies is crucial for an esthetician to ensure the safety and comfort of their clients during treatment. This information allows the esthetician to identify substances that may provoke an allergic reaction and tailor their services accordingly.

For instance, if a client has a history of allergic reactions to specific ingredients commonly found in skincare products or treatments, such as fragrances, preservatives, or active components, the esthetician can avoid using those products altogether. This proactive approach not only helps in preventing potential allergic reactions but also demonstrates the esthetician's commitment to client safety and personalized care.

While the other options provide some context about the client's lifestyle or preferences, they do not directly relate to the risk of allergic reactions as effectively as past allergy information does.