Allergy Tests

It is important to understand that the cornerstone of diagnosis of an allergy is a careful review of the history provided by the patient or their parent. If the history suggests that an allergy is present, then a simple allergy skin test can be used to help confirm or refute the suspicion. A positive allergy test in isolation shows only that there is potential for that particular allergen to cause symptoms when the patient is exposed to it. An example may clarify this point.  Imagine a person who grows up in an area of the world with very high grass pollen counts in the Spring and early Summer; in early high school years they develop typical allergy symptoms in that very season; as an adult they move to an area with low counts of grass pollen in the season and they no longer suffer with symptoms. If this individual were allergy tested, they would likely show a reaction to grass pollen.  In this case we would diagnose sensitization to grass pollen, but without current symptoms.                                      

We use a prick skin test method in the vast majority of cases. This procedure can help to confirm allergy to foods or environmental factors, such as cats, pollens, and moulds. Drops of allergen extracts are applied to the skin of the forearm (sometimes the back in very young children) and the skin is very lightly pricked, through the drops, with a special tool. This produces a very mild and brief discomfort that is not painful. After 15 minutes, positive reactions appear as small itchy hives, similar to mosquito bites. The reactions are measured and graded. All patients receive a printed report of the results.  After testing, Dr Cross will discuss the results with you and suggest a treatment plan.

The British Royal College of Paediatrics has produced two videos concerning allergy testing that demonstrate the technique that we employ for the prick test. The first shows testing of a young child, and the second demonstrates how we measure the responses and judge the validity of the results. See the videos, provided by YouTube, here. Be aware that several details will vary from our procedures, but the technique of testing is essentially the same.

© David Cross 2016