Olive leaf extract capsules are commonly used to increase your daily intake of antioxidants. Drugs.com states that olive leaf extract capsules do not have any reported cases of adverse reactions. Even though no reactions have been reported, taking any new supplement can cause an allergic reaction in your body. If you notice any common allergy symptoms after taking olive leaf extract capsules, call your doctor for a further evaluation. As with any allergic reaction, a severe reaction may occur.
An allergic reaction occurs when your immune system mistakes the olive leaf extract as a harmful substance that can pose a threat to your body. When this mistake occurs, the body quickly builds up a resistance against the supplement. The resistance consists of immunoglobulin E antibodies, histamine and other chemicals that attack the extract. The combination of these chemical releases causes various parts of your body to become swollen and inflamed. Most allergic reaction symptoms develop within a few minutes of ingesting the supplement but may take an hour or two before you notice any reactions.