There is little or no evidence that oilseed crops cause adverse reactions. First, the pollen is heavy (the plant wants insects to pick up and transfer the pollen grains) and the measured levels of airborne pollen is extremely low even a short distance from crop fields. Second, while it's faintly possible that volatile compounds emitted by the plants could be implicated, the evidence just isn't there. Take a look at this piece extracted from the BMJ, which looks critically at what evidence there is and which doesn't rely on received wisdom:

"The health effects of oilseed rape: myth or reality?" (That'll get you there).

I'm not a fan of oilseed rape because it creates a major pollen beetle problem and because it's a monoculture that relies heavily on chemical inputs. We have a farm near us that grows it over dozens of acres. There's a public footpath through the middle of it; last time I walked it when the crop was in full bloom the silence was eerie, no insects, no birdsong. But blaming it for allergies, etc., may be justified in rare cases for unlucky people only, just like lots of other things.