The methods used to diagnosis peanut allergies are very similar to those used in other food allergies. Physicians will generally start by asking a patient about their medical history and will perform a physical examination to rule out any conditions with similar symptoms. To better determine what type of food is the allergen, the physician will often have patients keep a food diary of everything they eat over a period of weeks or months. This will help demonstrate a correlation between a certain type of food and the onset of allergy symptoms.

• Skin test. This test involves scratching, pricking or injecting an individual’s skin with a peanut extract. The tested area will react with redness or swelling to indicate an allergic response. This test can be too dangerous to use on highly sensitive individuals. Recent research has helped to increase the effectiveness of this type of test when diagnosing peanut allergies.
  

  

• RAST (radioallergosorbent test). This blood test allows a laboratory to detect antibodies that correspond to a peanut allergy in a sample of the patient’s blood. While less accurate than skin testing, it can be used on those people who have reactions that are too sensitive for a skin test.
  
  
• Blinded food challenge test. This is considered the most effective way of determining the cause of a food allergy because it supplies the most convincing results. Different foods are placed within capsules to hide their identity. The patient consumes the capsules and the physician looks for signs of an allergic reaction. This type of test is time–consuming and difficult. It is often reserved to confirm suspicions that a patient's symptoms are not caused by a food allergy. This type of test should only be performed in the presence of a physician who can treat anaphylaxis.
  
  
• Elimination diet. This method involves removing peanuts from an individual’s diet for several weeks to see if allergic reactions persist. If symptoms stop, it can be presumed that peanut allergy was the cause. The food may then be briefly reintroduced to the patient’s diet in a controlled, clinical setting. If symptoms resume, the diagnosis of peanut allergy is confirmed.