Olive leaf extract capsules are commonly used to increase your daily intake of antioxidants1.Drugs.com states that olive leaf extract capsules do not have any reported cases of adverse reactions1.Even though no reactions have been reported, taking any new supplement can cause an allergic reaction in your body2.If you notice any common allergy symptoms after taking olive leaf extract capsules, call your doctor for a further evaluation1. As with any allergic reaction, a severe reaction may occur.

Allergic Reaction

An allergic reaction occurs when your immune system mistakes the olive leaf extract as a harmful substance that can pose a threat to your body1. 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 reactions2.

Skin Reactions

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Many times, your skin is the first organ to develop allergy symptoms. Your skin may become irritated, red and itchy within a few minutes of ingesting the olive leaf extract1. Common skin rashes that develop from an allergic reaction include hives and eczema, according to the American Academy of Allergy, Asthma and Immunology. Hives is the most common allergic skin reaction that causes the formation of welts in various clusters on your skin.Eczema is caused by a pre-existing condition that causes patches or dry skin and itchy blisters to form on your face, arms and legs.

Respiratory Reactions

Your respiratory system will be affected by the increased levels of histamine and IgE antibodies. Your lungs can become inflamed, causing swelling in the lungs and airways. Swollen airways can lead to trouble breathing, wheezing, coughing, chest pain and shortness of breath. If you feel a lump in your throat or you cannot breathe, call 911.

Digestive Reactions

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Your digestive system is primarily made of soft tissue. As the intestines become inflamed, you may develop various digestive complications. Common digestive symptoms include:

• diarrhea
  
• vomiting
  
• nausea
  
• cramping
  
• abdominal pain
  
• bloating

Digestive system reactions from an allergic reaction will not respond to common over-the-counter gastrointestinal medications2.