A careful and thorough history is the basis for the diagnosis and management of allergic diseases. Couple this with an examination and specific allergy testing, and you should have a complete allergy diagnosis.
Skin prick tests or blood (RAST or ssIgE) tests can be performed to help diagnose allergies – either by observing reactions on the skin or by measuring the amount of IgE antibody produced to a specific allergen in the blood.
These tests are often used to confirm a diagnosis of suspected allergy, and results need to be interpreted by an experienced allergy doctor or specialist. You should also be aware that a positive result does not necessarily mean you will react to that food or allergen. Again, a good history of the reaction after the exposure is the first step the assessment of allergies.
In the case of food allergy, your doctor may advise you to keep a food diary to help in the identification of food allergy. A food and symptom diary can be a very helpful tool for you too. You may wish to consider starting one before you see the allergy specialist or GP so you have a written record of diet and reactions for your first visit. Over a period of a week or two, a pattern may emerge. It is important to note that if a reaction to a particular food is severe, avoid that food in question until you have consulted your doctor.
Skin Prick Tests
Skin prick tests may be carried out on patients of any age, including infants.
They are reliable involving small drops of the “allergen” being placed onto the forearm or back, then the skin is pricked to allow a tiny amount of the allergen through the skin. Reactions are then measured and reported at standardized time.
Here at Waikato Allergy Clinic we perform skin prick tests to a wide range of allergens.
Blood Tests (RAST or ssIgE)
RAST tests are blood tests used to measure the amount of IgE (antibody) that is directed to a specific allergen.
The major advantages of RAST tests are that they do not run any risk of an adverse allergic reaction and should give similar information to that of a the skin prick test.