There are two main sorts of tests that I do. One is skin prick testing and the other is blood testing.

With skin prick testing what we do is...I've got a batch of little bottles of allergens and these range from foods through dusts and pollens to things like cat hair and dander. I will choose the ones that I think are most likely. We put little drops on the patient's arm and then we gently prick the skin with a sterile needle through each drop to try and bring a little bit of the allergen into the skin because the skin is one of the most sensitive areas. And what we're looking for are little reactions wherever there's a positive response to the allergen.

The other sort of test that we do is a blood test. The blood tests are simpler to do because it just requires taking a small sample of blood but the person doesn't get it back right away. They have to go off to the lab. What we're looking for are the levels of the antibodies in the blood against the allergens that we're testing for. We give the lab a list of perhaps half a dozen of our number one suspects and they come back and they tell us the levels of antibody against each of them and we can use that to confirm the clinical impression that the person is sensitive to that particular thing.

The problem there is what we get is ones where you've actually got positive reactions to the allergen but it doesn't necessarily mean that that's what's going to be responsible for your symptoms. So we do it the other way round. We look at your symptoms, we look at what we think are causing it and we use the tests to confirm that.