If it is the pollen from rape seed pollen that is causing the allergy, there is no point eating honey say that has been made from the collection of say tree pollen. If you contact someone who can assure you the likelihood of their honeybees have fed from Rape pollen, this should give you positive results. I worked with a agricultural fencing contractor ( who also had a small flock of sheep) in the Midlands area. He would only buy local honey and eating local honey could mean the difference between wearing a full faced fan filtered helmet when hay making or not. Their may not be scientific evidence to support the benefits of eating honey. But many people do rely on it for relief. Do the research, buy local, see if it helps. Good luck. I suffered for many years as a kid with hayfever. Now it's one or two sneezes a year if I'm unlucky. But that is down to medical intervention some 40 years ago or just growing out of it.