Side effects of olive leaf extract A potential side effect of taking olive leaf extract is allergic reactions. The extract comes from the olive tree, so some people may be allergic to it.

Side effects associated with olive leaf extract are rare and mild, but allergies are possible. Always talk with your healthcare provider before taking any new supplement.

Is olive leaf extract toxic? No, there seem to be no reported toxic effects of eating or drinking olive leaf extract.

Olive leaf extract may reduce blood pressure, improve blood lipids and help the way our bodies handle glucose. But the evidence isn’t clear cut.