Olive Leaf Extract's active component is a phenolic compound known as oleuropein. Oleuropein (pronounced oh-lee-or-oh-pin) is a bitter substance that scientists have isolated from the olive leaf. It was found to be part of a compound produced by olive trees that make them particularly vigorous and resistant to insect and bacterial damage.

Oleuropein's antimicrobial activity occurs when it breaks down in the body to elolenic acid. The elolenic acid interacts with a target pathogen at a receptor, as a key interacts with a lock. The elolenic acid interferes with the replication process of most pathogens. Once the extract begins to affect the pathogens, the immune system may renew itself to do its job to protect the body from disease.

You can't cold process olive leaf extract and pull out all the necessary phytochemicals to make it synergistic. Many of the other phytochemicals are also fungicidal or bactericidal. The preparation of the extract requires careful processing in order to maintain full activity. This also makes the product more expensive. There continues to be controversy between companies claiming that their product is better than others, so you should use a reputable brand. Some companies challenge the idea that a higher percentage of active ingredient (typically in the range of 6-12%) is more effective.

Olive Leaf Extract may be effective against viruses, retroviruses, some bacteria, parasites, yeasts, protozoan and some skin fungi like tinea versicolor.

Some people experience what is known as a Herxheimer reaction or "die-off" when taking olive leaf extract in large doses. This is a detoxification reaction. If you experience greater fatigue, diarrhea, headaches, muscle/joint aches or flu-like symptoms, temporarily discontinue taking olive leaf extract or cut back on the amount taken until the symptoms subside. This effect is not commonly seen when starting with a low dose.

A person with a known bacterial or yeast infection, should start taking the olive leaf extract slowly. Perhaps 1 capsule twice a day for 3 days and then 3 times per day with meals. If a person is doing well then increase the dosage so that you're taking at least 4 - 6 capsules (500mg) per day.

It is important to take lots of water during this time to ensure organism breakdown products don’t accumulate in the kidneys.