The nursery sector is just so low-paid that, as some people have pointed out, people would just avoid going into it altogether if there is even the slightest possibility of ending up with a criminal record or a prison sentence, just through a one in a million incident that could happen because of things that are essentially out of the hands of the individual concerned: inadequate staffing ratios; having to accept too many children with extra needs where the provision is inadequate to safely cope with them; a catastrophic series of events on any given day that is out of an individual's hands which they know means the setting is operating with more risk than usual but what choice do they have?
The fewer people that go into it the higher the salaries will need to be to fund it. And if there just isnt' the money there to fund those salaries then the ultimate outcome will be that highly allergic children sadly become liabilities to childcare settings and one that a standad nursery would just not be willing, OR ABLE, to take on.
And you'd end up with the ultimate in "othering" - specialised childcare settings for allergic children, which cost more to run because the supervision ratios are much better and the staff are allergy specialists etc.