In many cases, symptoms of allergic reactions are difficult to differentiate from other illnesses such as colds or food intolerance. Because of this, it is recommended that allergies should be diagnosed by an allergist to avoid taking inappropriate medications.

Diagnostic evaluation of a person with suspected allergic disorders begin with a comprehensive medical history and physical evaluation. Important points such as family allergies, previous allergy tests, habits, and the time and setting where the symptoms usually occur are also assessed and documented.

Apart from the physical and lifestyle evaluation, the doctor will also verify the presence of the allergic disorder through skin tests, blood tests, and radioallegosorbent test.

SKIN TESTS
Methods of skin testing include:

• Prick test/ Scratch test

Also called puncture testing, this method involves a small amount of allergen dropped onto the skin (usually the forearm or back). With the use of a lancet, the skin is scratched or pricked through the liquid to introduce a safe amount of the allergen.

• Patch test

This uses a large adhesive patch that contains various allergens all over it and applied at the back for 24-72 hours. The person undergoing the test should avoid having exercise or bathing to avoid interference with the test results.

• Intradermal skin test

After prick testing, intradermal skin testing is performed with allergens that did not elicit positive reactions. The skin is penetrated superficially and a small amount of purified allergen solution is injected to create a bleb (raised area).

Interpretation of Results:
A positive reaction is elicited once the area tested displays a diffuse redness (erythema) and swelling. These reactions are indicative of sensitivity to the corresponding allergen.

To prevent false-negative results, medications that suppress allergic/inflammatory reactions (e.g. antihistamine, corticosteroids) are withheld 2-4 days before testing.

BLOOD TESTS

• Eosinophil Count

This may be obtained in from blood samples or smears of boy secretions. An increase in the eosinophil (a type of white blood cell) is suggestive of an allergic reaction however, not confirmatory.

• Total Serum IgE

This test determines the amount of antibodies produced in response to an allergen. Increased levels of Immunoglobulin E support the diagnosis of hypersensitivity disorders.

RADIOALLERGOSORBENT TEST

The RAST determines the specific type and amount of allergen to evoke an allergic reaction. The test is absolutely safe and there is decreased risk for systemic reaction as it is performed outside the patient’s body. However, RAST have limited allergen selection. Results aren’t immediately relayed and it costs a lot.