This consists of keeping a chronological record of all foods eaten and any associated adverse symptoms. It is an inexpensive endeavor that documents the frequency of symptoms and their occurrence in relationship to food ingestion. In addition, it encourages patients to focus on their diet.
This record is occasionally helpful for identifying the food implicated in an adverse reaction; however, it is not usually diagnostic, especially when symptoms are delayed or infrequent.
Occasionally, review of the diet diary reveals that the patient is not experiencing a reaction even when eating, as an ingredient in other foods, a significant amount of a food to which they were thought to be allergic.
This is used in determining the diagnosis as well as in the treatment and prevention of food allergy.
When used as a diagnostic tool, the elimination diet requires complete avoidance of suspected foods or groups of foods for a given time period (usually 7-14 d) while monitoring for an associated decrease in symptoms.
Success depends on identifying the correct food allergen and completely eliminating it in all forms from the diet. These diets are increasingly difficult to develop and follow as more foods or foods that commonly occur in the diet are eliminated.
Additional limitations of this method include potential effects of patient or physician biases, variable patient compliance, and the time-consuming nature of the endeavor.
When the elimination diet is used as treatment, identified food allergens are removed from the diet indefinitely unless evidence exists that the food allergy has been outgrown.
Prick and puncture tests are the most common screening tests for food allergy and can even be performed on infants in the first few months of life. However, the reliability of the results depends on multiple factors, including use of the appropriate extracts and testing technique, accurate interpretation of the results, and avoidance of medications that might interfere with testing (eg, antihistamines).
When used in conjunction with a standard criterion of interpretation and appropriate controls (eg, histamine: positive, saline: negative), these tests provide useful and reproducible clinical information in a short period (ie, 15-20 min) with minimal expense and negligible risk to the patient.
This is a reliable method of excluding IgE-mediated food allergies. The negative predictive accuracy is greater than 95%; however, the positive predictive accuracy is generally less than 50%, which limits clinical interpretation of positive skin test results.
Positive skin test results, in addition to the suggestion of clinical reactivity based on the history, must often be confirmed by an oral food challenge unless the patient has a thoroughly convincing history of significant food allergy.
Intradermal skin testing
The risk of inducing a systemic reaction with this type of testing is increased in comparison to the prick or puncture method; as a result, intradermal skin testing should be avoided.
In addition, the results obtained by using this method are less specific compared to those obtained by using prick or puncture testing.
Tests with uncertain diagnostic value: The diagnostic value of performing the following tests is not currently supported by objective scientific evidence:
Results from food-specific immunoglobulin G (IgG) or IgG subclass antibody concentration testing have not been proven to be helpful with diagnosis.
Testing for food antigen-antibody complexes has no proven diagnostic value.
Performing leukocyte cytotoxic tests is not supported by objective scientific evidence.
Results from subcutaneous provocation and neutralization testing have not been proven to be helpful for diagnosis.
Kinesiology-based testing is not recommended because objective scientific evidence has indicated this type of testing does not aid in diagnosis.