“I can see why [the SSWP] wished to say that on the facts the tribunal ought to have found that once you take into account such ordinary precautions as might reasonably be expected, including carrying the epi-pen, against the limited possibility of severe anaphylactic shock, and once you take into account screening out occupations with obvious exposure to rubber and latex, the risk to health should be found not to be substantial. That however is a question of fact in each case. It was not a question of law on appeal of the Upper Tribunal and it is not a question of law here”