Glycerin Borax is used in the treatment of mouth ulcers and inflammation as paint for the throat and tongue in children and to reduce dryness of mouth. Glycerin Borax Mouth Ulcers Glycerin borax is effective in the treatment of mouth ulcers. The application of the medication on the area helps to relieve pain and reduce stinging. Glycerin Borax is safe to use to clean the mouth of babies. Glycerin has a naturally sweet taste but does not cause tooth decay.