Skin Prick Testing
It should be noted however that in determining allergic status, the history taken on consultation is of utmost importance.
A skin prick test is an easy way of determining whether your child has allergic antibodies (IgE) to a particular allergen. As such, the test is very useful for IgE-mediated disease, such as an immediate allergic reaction to a food. Generally this type of reaction to food occurs within a few minutes, up to roughly 60 minutes.
The skin prick test is also very useful for testing for allergy to an environmental allergen (for example to pollen or house dust mite in a patient with allergic rhinitis). It should be noted that a skin prick test is not a good screening test but is very useful for confirming allergy, for example to a food, and is useful in monitoring for potential resolution of food allergy.
Results from a skin prick test are not related to severity of reaction to a particular food or risk of anaphylaxis. The level of reactivity (wheal size) on the skin prick test is related to the probability that your child will have an allergic reaction to a particular food. One subject can have a small wheal on a skin prick test and have a background of anaphylaxis whereas another subject can have a very large wheal size but have a relatively minor reaction if the food in question is eaten. As such, the history taken at time of consultation is of utmost importance in determining risk of reaction together with relevant risk factors such as past anaphylaxis, co-existing asthma and type of food and amount to which a subject has reacted.
A large number of common allergens are available in the clinic as commercially prepared preparations. For unusual allergens we ask that a small amount (around the size of a 20 cent piece is sufficient) is brought on the day of consultation. For seafood in particular, it is best to bring a small amount of fresh and cooked sample for skin prick testing as the commercial preparations for seafood can be falsely negative.
Results of skin prick testing will be available during the consultation.