The hazards and side effects of dental whiteners include damage to teeth, tooth sensitivity, pain and discomfort, and damage to gums. 1. The dental instrument uses cold light whitening, which will cause enamel scratches on the surface of the teeth during the whitening process, damaging the enamel and causing damage to the teeth, making them lose their original natural luster. If there are porcelain teeth in the mouth, it may cause the problem of chipping. 2. Cold light whitening is a high concentration of zinc oxide as a whitening agent, redox reaction on the teeth have chemical damage, whitening is easy to dentin sensitivity, teeth will be sore. 3. Dental instrument is not recommended for personal use, because the power of the dental instrument is not stable, non-professionals are prone to improper operation, not only can the above hazards, and in severe cases, even damage to the gums resulting in gingival recession, pulpal inflammation, pain and discomfort and other adverse consequences. If there is a need to whiten teeth, it is recommended to go to the hospital, under the guidance of the doctor for formal treatment.