By Dr Samantha Walker, Director of Research and Policy at Asthma UK
Many people believe they have an allergy, but there is plenty of data to suggest that a lot of people think they’ve got an allergy when they haven’t.
For example, while 10-12 per cent of the general population think they have some type of food allergy or intolerance, blood or skin prick tests only confirm an allergy in 1-2 per cent of them. The problem is that the only way to confirm an allergy is to have a skin prick or blood test at a clinic, but these can be difficult to arrange on the NHS or expensive if arranged privately.
Working with a team at the University of Edinburgh and the University of Bristol, we wanted to see whether we could develop a simple questionnaire which could rule out potential food (or indeed other) allergies in some people, to prevent them having to undergo more time-consuming tests or unnecessarily avoid certain foods.
We recruited 143 people and asked them to fill out a questionnaire with ten questions related to triggers, allergy symptoms and family history. Participants were then given skin prick tests for a number of allergens including house dust mites, grass, dog and cat allergens, and divided into groups depending on whether they showed positive or negative responses to allergens.
By checking the answers to questions against the group which did not reveal any allergic responses to the skin prick test, we found a set of four questions could be used to predict with around 88 per cent accuracy that someone would not show an allergic response to the test.
The four questions were:
- Do you have, or have you ever had, hay fever?
- Do your allergy symptoms vary when you go from place to place (for example, on holiday)?
- Do any of your parents or siblings have, or have they ever had, hay fever?
- Is there a specific trigger that always sets off your allergy symptoms?
Essentially, what this means is that if you think you’ve got an allergy, but you answer ‘no’ to these four questions, then you would have negative reactions if you were tested using skin prick or blood tests almost 90 per cent of the time. This is useful to know because if you have negative skin prick or blood tests, you would be extremely unlikely (occurring less than 1 per cent of the time) to be allergic to food, or indeed have any other types of allergies.
This doesn’t mean that this will be true all of the time, and a consultation with your GP or practice nurse or referral to an allergy specialist might still be useful if you are at high risk of having an allergy. Our health advice pages provide more information for people with asthma on food and pet allergies and other triggers such as pollen.
This study, published today in the British Journal of General Practitioners, is based on a small group of people. We need further research with a larger number of people to confirm whether this set of questions could be used as a screening tool in the future.
Much more research is needed to better understand the links between allergies and asthma. It’s only through support like yours that we can continue to support this kind of research.