Eva is a 19-year-old woman with a known grass pollen and house dust mite allergy. However, one day she ate an Asian dish containing nuts, coconut milk, chicken, vegetables, and rice. After dinner, she had to vomit and suffered from diarrhoea.
As I'm sure we've all experienced before, the first thing you usually think of when you have a gastrointestinal illness is the last meal you had, and that the symptoms have something to do with it.
She therefore informed her doctor, who then carried out a singleplex IgE blood test. He decided to screen her blood for serum IgE antibodies against almond, hazelnut, peanut, coconut, Brazil nut. According to the singleplex IgE test, Eva was positive to all tested nut varieties. The doctor told her to avoid nuts completely and to always carry an emergency kit with her.
However, to confirm her diagnosis, a skin prick test and an oral food challenge was performed. The skin prick test was positive only for grass pollen and house dust mites, but negative for all nuts. During the oral challenge, Eva had to consume small quantities of several types of nuts, but again, no symptoms developed.
The doctor wondered: “Where do these discrepant results come from?”
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The doctor was already very interested in molecular allergology at the time and came across our test. He contacted us and we offered him to send us Eva’s serum for testing. In the ALEX2 Allergy Xplorer, the results revealed IgE sensitisation to grass pollen and house dust mites, confirming the results of the skin prick test. In total 10 clinically relevant sensitisations were detected, but all tested nut allergens were negative. I think you can imagine how relieved Eva was when she got the message that she is not allergic to nuts. Her gastrointestinal problems may have come from a viral or bacterial infection.
Experimentally, we repeated the test without a blocking step, and positive signals jumped from 10 to 110 including peanut, hazelnut, walnut, almond, etc.
WHY are the nuts negative in the ALEX² with the blocking step (which is automatically included in our test by default) but suddenly positive in the ALEX² Allergy Xplorer without the blocking step? Curious?