Oddly, on continental Europe, where oilseed rape is a major crop, no such concerns are aired. Poor old oilseed is incredibly conspicuous when in flower and it has a strong aroma too. But it flowers when much tree pollen is still being released and it is still in flower when the grass pollen season kicks in. It can be attacked by fungi which release billions of spores, a possible suspect. Basically, there's too much else going on when rape is in flower to directly implicate its pollen in causing harm.

As I said, I don't like this crop plant. It requires huge inputs of nitrogenous fertiliser and it needs several treatments with fungicides and insecticides. You'll always see those tractor tracks in its fields. It can never be grown as an organic crop and it's a major monoculture culprit. Along with maize (my personal most hated crop), it is responsible for much nitrogenous runoff into waterways. And when it's grown anywhere near me I get a plague of slugs and pollen beetle. So I'm not sticking up for it, but the CPS wouldn't dream of prosecuting it for causing allergies, what with the complete lack of anything other than anecdotal evidence!