Grapefruit (citrus paradisi) is a member of the Citrus family. Grapefruit seed extract is processed from grapefruit seeds and pulp obtained as a byproduct from grapefruit juice production.
Always be aware that grapefruit seed extract is very concentrated. Wash your hands after you have handled it, in order not to accidentally rub your eyes.

In the years since its discovery, grapefruit seed extract has been tested and validated by the FDA, USDA, the Pasteur Institute in France, and numerous physicians. The active ingredient of grapefruit seed extract is non-toxic and is synthesized from the seed and pulp of certified organically grown grapefruit.
Grapefruit seed extract is a strong disinfectant for a wide range range of microbes. It will also kill bad bacteria in the intestines, but not harm the good ones. One in a while we take it internally (one or two drops in a glass of water) when we feel that a "buggie" is bothering us. Sometimes I gargle with it for a sore throat and sometimes I use it just to clean my mouth as bacteria offer linger in the mouth. It can also be used on the skin.
We use it mostly to disinfect veggies. The veggies are placed in a bowl of water, with 2 or 3 drops of grapefruit seed extract.

 
Grapefruit seed extract is available at your local health food store or at http://www.nutribiotic.com/  .

Apparently grapefruit seed extract can react with certain prescription medicines.
The material in this site is provided for educational and informational purposes only, and is not intended to be a substitute for consultation by a healthcare provider. Please consult your own physician or appropriate healthcare provider about the applicability of any opinions or recommendations with respect to your own symptoms or medical conditions.