I have been using H2O2 for several years. I put 3% on my tooth brush and then paste and brush regularly, followed by a fresh water rinse. This had cured my bleeding gums and haven't had a cold in the last 4 years.
Have used food grade 35% for killing skin cancers. Here you must be very careful as it burns the cancer. I found that applying, with a Q tip every other day for about 5 - 6 days kills the cancer. In 2 weeks the scar is gone and the skin is normal.
All, have a healthy and happy New year.