The methods used to diagnosis seafood allergies are very similar to those used in other food allergies. Physicians will generally start by asking a patient about 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 the patient keep a food diary of everything eaten 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.

When a specific type of seafood is already suspected as an allergen trigger, it can be relatively simple to diagnose a seafood allergy. The most basic question a physician will ask is whether an individual has a consistent reaction to a type of seafood each time it is consumed.

To be sure that seafood is the allergen, a physician will often administer one or more of the following tests:

• Skin test. Involves scratching, pricking or injecting an individual’s skin with various seafood extracts. The tested areas will react with redness or swelling to indicate an allergic response. Skin testing can help to identify or disqualify specific types of seafood allergens. However, it can be too dangerous to use on highly sensitive individuals.
  

  

• RAST (radioallergosorbent test). A blood test for antibodies that correspond to a specific seafood allergy in a sample of the patient’s blood. Though 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. 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 be performed only in the presence of a physician who can treat anaphylaxis.
  
  
• Elimination diet. Involves removing all seafood from an individual’s diet for several weeks to see if allergic reactions persist. If reactions stop, it can be presumed that a seafood allergy is present. Seafood may then be briefly reintroduced one-by-one to the patient’s diet under a physician’s supervision. The diagnosis of a seafood allergy is confirmed if and when symptoms resume.