Spadlet, you shouldn’t feel sinful about Google, but you do need to be discriminating. If you want to find scientific research, Google Scholar is a better place to begin.
Dealing with the website you found. Despite its web address, this is a private website with no endorsement from Government or the scientific sector. This private individual has a view that oilseed rape causes respiratory illness. A search of PubMed (the most complete directory of medical literature) produces information on the following connections with allergy:
1) Food allergies. Canola seed contains 2S albumins that produce a skin-prick reaction on some children with food allergies. These are known allergens from many seeds. Nut allergens belong to this class, for example. Children with this sensitivity were frequently sensitive to a wide range of foods. This suggests the skin-prick reaction to rape and turnip seed is more likely a cross-reactivity than produced by exposure to rape seed per se.
Sensitization to turnip rape and oilseed rape in c...[Pediatr Allergy Immunol. 2008] - PubMed Result
Napins, 2S albumins, are major allergens in oilsee...[J Allergy Clin Immunol. 2006] - PubMed Result
Turnip rape and oilseed rape are new potential foo...[Allergy. 2006] - PubMed Result
2) Rape pollen contains proteins with similarity to those in grass pollen that produce reactions in sera tests. Similar proteins will be found in all pollens. So potentially all pollens are plausible allergens.
Identification of allergens in oilseed rape (Brass...[Int Arch Allergy Immunol. 1998] - PubMed Result
Oilseed rape pollen is a potentially relevant alle...[Clin Exp Allergy. 1997] - PubMed Result
Identification of oilseed rape (Brassica napus) po...[Int Arch Allergy Immunol. 2003] - PubMed Result
In reality, the incidence of allergy to pollens is therefore dependent on exposure. Pollen present in the air will be much more likely to create an allergic reaction than pollen that is rarely present in the air. Epidemiological studies (as opposed to lab sera studies) indicate that allergy to oilseed rape pollen is very rare, mostly associated with allergies to other pollens and generally limited to those with occupational exposure. Canola pollen is rarely found in air measurements, except within a field.
Oilseed rape--a new allergen? [Clin Exp Allergy. 1992] - PubMed Result
Oilseed rape and seasonal symptoms: epidemiologica...[Thorax. 1994] - PubMed Result
Allergy from occupational exposure occurs occasionally with vegetable growing and also occurs with broccoli and cauliflower for example. Those working in the fields get more opportunity for exposure.
Brassica oleracea pollen, a new source of occupati...[Allergy. 2006] - PubMed Result
The majority of the concern that oilseed rape may present an allergy problem is centred in Scotland. A search of PubMed for allergies connected with canola (what the rest of the world calls this crop) yielded a single reference of importance, the same as one of the oilseed rape references.
I mentioned previously that oilseed rape/canola produces glucosinolates that become degraded into isothiocyanates on cell destruction. It is possible to generate respiratory symptoms (similar to those in the picture illustrated on the website) by crushing the leaves of the plant and rubbing the extract into your eyes or nasal passages. Children playing in oilseed rape crops may expose themselves to concentrations of isothiocyanates sufficiently high to get a reaction. Equally, children playing in wheat crops may get nasty skin rashes from the edges of the leaves.