To treat herpes with olive leaf extract, drop 1 to 2 droplets on a cotton ball and place on the sore. One study found that olive leaf extract’s antiviral and antimicrobial factors reduce the ability of the herpes virus to invade surrounding cells.

Oleuropein is also shown to have a protection against Alzheimer’s disease. The antioxidant effects of olive leaf extract may also help with preventing damage or loss of dopamine neurons that’s associated with Parkinson’s disease.

Researchers believe olive leaf extract can have positive effects on atherosclerosis, or narrowing of the arteries, which is the highest risk factor for heart disease. High levels of LDL and total cholesterol are risk factors for developing this disease. One animal study from 2015 assessed the effects of olive leaf extract on cholesterol levels. Rats who took the extract for eight weeks had significantly decreased cholesterol levels.

Olive leaf extract may help lower systolic and diastolic blood pressure. A 2017 study found that olive leaf extract successfully lowered blood pressure. A lower blood pressure can reduce your risk of stroke and heart attack.

A review of olive leaf extract and type 2 diabetes found that olive leaf oil extract can help improve insulin secretion in cells. Animal studies have shown that olive leaf extract may:

• reduce hyperglycemia (high blood sugar)
• reduce hyperinsulinemia (too much insulin in the blood)
• reduce blood glucose, plasma malondialdehyde, and other signs of oxidative stress (an imbalance of free radicals that can harm the body)
• reduce cholesterol
• decrease serum glucose
• increase serum insulin

One human study found that people who took olive leaf extract tablets lowered their average blood sugar level and fasting plasma insulin levels.

An animal study from 2014 researched the effect of olive leaf extract in preventing high-fat, diet-induced obesity. It’s thought that olive leaf extract prevents obesity by regulating the expression of genes that affect weight gain. It can also aid in reducing food intake.

In one cell study, olive leaf extracts were shown to stop cancerous cell growth. Researchers suggest that the extract has strong antioxidant properties, but this is also one of the first studies on olive leaf extracts and their anticancer effects.

Agencies like the Food and Drug Administration don’t regulate nutritional supplements like olive leaf extract. Because olive leaves have been an important part of the Mediterranean diet for centuries, the extract is considered safe for most people.

It’s possible to develop severe respiratory allergic reactions. Some people are allergic to the pollen produced by olive trees and may have an allergic reaction.

Olive leaf extract may lower your blood pressure and blood sugar levels. If you have diabetes or are taking medications to manage your blood sugar or blood pressure, talk to your doctor before taking olive leaf extract.