Grapefruit seed extract (Citrus paradisi) was first employed as an antimicrobial agent and disinfectant within the agriculture industry. It has also been widely used in veterinary medicine as a panacea. The most common commercial preparation is Citricidal. Because of its broad antimicrobial action, grapefruit seed extract has been explored for its potential therapeutic use against conditions caused by bacteria and fungus.
Grapefruit seed extract has also been shown to exhibit certain antibacterial, antifungal, and antioxidant activities. The primary constituents found in grape seed extract include the polyphenolic compounds: hesperidin, neohesperidin, and naringin.  These compounds exist in the classification of flavonoids and give grapefruit seed extract its anti-oxidant activity. 
The exact mechanism for its antimicrobial activity has been discovered in research studies. The grapefruit seed extract actually disrupts the bacterial cell membrane, causing the cytoplasmic contents to leak out.  The entire process occurs in approximately 15 minutes. Grapefruit seed extract is thought to be effective at killing over 800 strains of bacteria and some 100 strains of fungi.
Grapefruit seed extract is derived from the peel, pulp and seed of the grapefruit.
Grapefruit Seed Uses
There have not been any formal research studies testing the efficacy of grapefruit seed extract against specific infections or diseases in humans or animal models. Because of the well-accepted antimicrobial activity of grapefruit seed extract, its use has been extrapolated for the following conditions: 
- Grapefruit seed extract may be helpful for vaginal Candida and intestinal Candida. Grapefruit seed extract is effective at killing Candida species in vitro, and its use for the aforementioned conditions has been supported by anecdotal reports.
- Grapefruit seed extract may be helpful for cases of infectious diarrhea cause by different strains of bacteria; including those associated with food poisoning.
- Grapefruit seed may be effective at killing bacteria that are associated with the development of ulcers in the stomach such as H.pylori.
- Grapefruit seed extract may be effective for infections in the mouth and gums caused by bacteria or Candida. It has been used as a gargle or rinse with positive results from anecdotal reports.
- Grapefruit seed extract can also be applied topically for uses as a local disinfectant and antimicrobial for cuts and abrasions. It should not be applied to open wounds.
Grapefruit seed extract is very potent and toxic in its undiluted form. It has been found effective and non-toxic at a dilution of 1:512, though most recommendations for use are a 1 - 2% concentration.
- Capsule: 100 - 200 milligrams per day with meals
- Drops: 5-10 drops per day with meals
- Rinse: 5-10 drops in 2 ounces water (30 second ‘swish’ and spit)
Again, the undiluted form is toxic to cellular membranes and will cause a serious reaction if oral ingestion or topical application occurs (e.g. skin irritation).
Grapefruit seed extract is toxic in its undiluted form. Its use in pregnant or nursing women has not been studied, and its use in this population should be avoided.
1. Cvetnic Z, Vladimir-Knezevic S. Antimicrobial activity of grapefruit seed and pulp ethanolic extract. Acta Pharm. 2004 Sep; 54(3): 243-250.
2. Giamperi L et al. Antioxidant activity of Citrus paradisi seeds glyceric extract. Fitoterapia. 2002 Mar; 75(2): 221-224.
3. Heggers JP et al. The effectiveness of processed grapefruit seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity. J Altern Complement Med. 2002 Jun; 8(3): 333-340.
4. http://www.pdrhealth.com/drug_info/nmdrugprofiles/herbaldrugs/101840.shtml Grapefruit seed extract. February 2005.