Grapefruit Seed Extract is one of the most powerfull natural remedy against Candida - The Yeast Syndrome.
The Yeast Syndrome is usually caused by overuse of Antibiotics , but some researchers link it to different parasitic animals.
It is hard to say who came first, Candida, or parasites.
If you are using Grapefruit Seed Extract, you should also use home made yogurt or some other source of probiotics, because larger amount of Grapefruit Seed Extract can aslo kill intestinal flora.