Allergy tests, are they a waste of money?
Allergy testing has become increasingly popular over the years, in fact we see a lot of people at Elan Medical Skin Clinic who claim that they have been diagnosed with certain food intolerances. But how reliable are these tests?
The medicines regulator (MHRA) has said there is no scientific basis for tests widely available in health food shops and pharmacies that claim to show food intolerances. In fact the MHRA found that there was “no scientifically valid test to diagnose food intolerance”. Many of the tests confirm the presence of IgG antibodies, which show only that a food has been eaten at some stage, not that someone is intolerant of it!
The MHRA said that attempting to self-diagnose a food intolerance or allergy using a test kit alone could potentially result in a delay in identifying or treating other medical conditions. It added that there was a clear distinction between food intolerance and food allergies, which can be potentially life-threatening.
So what should I do if I think my child has a food allergy?
Before you make big changes to your child’s diet or your own diet, it’s important to proper medical advice, so talk to your GP. If you or your child suffers from severe eczema, there are allergy specialist that you can be referred to on the NHS. If you GP is reluctant to refer, then book in to see Sue Ibrahim at Elan Medical Skin Clinic.
All forms of allergy testing, even when the results seem to be strong, must be considered together with a physical exam and a detailed patient history – both of which can help narrow down what food might be the trigger.
“You have to look at all the pieces of the puzzle because none of the tests by themselves are predictive enough of a diagnosis of a clinical allergy,” Sue Ibrahim says.
The physical exam and patient history also provide important clues, such as symptoms that could indicate whether or not a food allergy is the likely cause.
If you have hay fever you probably don’t need allergy testing as it may be obvious from your symptoms that you’re allergic to pollen. But it’s important to find out the precise cause if your symptoms are more complicated.
For example, perenial rhinitis, – a runny nose all year round – can be triggered by a variety of allergens, such as house dust mites and mould, or a food allergy could be triggered by one of a number of foods in your diet.
Allergy testing can also help monitor a diagnosed allergy. For example, babies and children with certain food allergies often grow out of them.
A test can let the parents and child know they no longer have an allergy to milk or eggs for example, so they no longer have to avoid that food.
Skin-prick testing (SPT) is the most common form of allergy testing and is used to try and identify the specific foods that a patient may be allergic to. Theses tests are only carried out at specialist medical allergy centres and if Sue Ibrahim thinks that you or your child should be referred to for allergy testing, she will refer you.
What is a skin prick test?
Drops of different serums containing individual allergens will be put the on patient’s forearm or back. A medical professional will then use a small needle to prick the skin – this feels like a small poke with a pin – so that the serum goes beneath the skin.
Skin prick allergy tests are only ever carried out by medical professionals specialist allergy centres.
Then it’s a waiting game. The patient’s skin may react by forming a reddish hive, or wheal, at specific prick spots, indicating that the IgE antibodies in the skin responded to the food allergen in that serum.
A test is considered “positive” for a particular allergen if the diameter of the hive is 3 millimeters or greater than a prick site made with no allergen (known as the negative control). The bigger the hive, the more likely it is that you will react if you eat that food.