The methods used to diagnosis tree nut allergies are very similar to those used to diagnose 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 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.

Other diagnostic methods may include:

• Skin test. This test involves scratching, pricking or injecting an individual’s skin with a tree nut extract. If the tested area reacts with redness or swelling, it may indicate an allergic response. This test can be dangerous for individuals with severe tree nut allergies.
  
  
• RAST (radioallergosorbent test). This blood test allows a laboratory to detect antibodies in a sample of the patient’s blood that may indicate a tree nut allergy. It can be safely used on people who have severe allergic reactions.
  
  
• 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 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 tree nuts from an individual’s diet for several weeks to see if allergic reactions persist. If symptoms stop, it can be presumed that tree nut 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 tree nut allergy is confirmed.