1. Buy a purple light or a money detector.

2. Choose the night to test, turn off the indoor lights, showing a completely dark state.

3. Disassemble the mask and illuminate the mask with a purple light or a money detector.

4. If the mask has fluorescent whitening agent, it will reflect light slightly.

5. You can also smear the essence of the mask on your hands and illuminate it with a purple light or a money detector to see if there is reflection.

Please note that the above methods are only suitable for judging whether the mask contains fluorescent whitening agent, and cannot guarantee its whitening effect or other quality indicators. If you are in doubt about the product quality, it is recommended to consult a professional organization or directly contact the product manufacturer. At the same time, before using any product, especially the product applied to the skin, please ensure its safety and applicability.