Our Colloidal Silver 500 ppm is a pharmaceutical grade. It is safe and effective. Can be used on humans of all ages, pets and farm animals. .002-micron size. Our Colloidal is 99.9% Silver! We have field tested it here for years and have had NO negative reports, only success stories. Dose: Adult - 1/2 teaspoon in any liquid once daily. For severe infections can be taken 2-3 times a day.