Gideon Lack was the main person doing research into the use of peanut oil and the link with an increase in allergies. (Brief summary \link{http://www.alspac.bris.ac.uk/press/peanut_allergy_press_release.shtml\here}) The annoying thing is that despite this research, hospitals still use creams etc. using peanut oil on very small babies.
The Surrey Allergy Clinic say the rise in nut allergies may simply be due to more people in the UK eating tropical nuts. They also point to a link with higher incidence of hayfever and that more male Birch trees are being planted in Britain, and the male trees produce loads of pollen. They say that hayfever sufferers being treated by birch pollen immunotherapy have found up to 80% of their oral allergies being resolved.
I think there is a lot in the hygeine hypothesis, mentioned by williamsmummy, but I also think one culprit is increasing processing of food and use of additives. Despite recent changes by Birds Eye and the like, food we buy in the supermarkets tends to have all kind of additives that have been changed beyond recognition from the source foodstuffs. So if we buy 'snack eggs' or 'fish fingers', our exposure to, say, soya proteins, milk proteins, or the particular ingredients used as food colourings, is far higher than it would be if we just bought sausage meat or fish ourselves and rolled them in breadcrumbs. Similarly, a bag of crisps is unlikely to just contain potatoes and oil, but also preservatives, artificial flavours and flavour enhancers, all of which I suspect have only been on the scene for less than 50 yrs.
Of course some of this may just lead to food intolerances rather than allergies, but I think it must have some contribution to the rise in sensitivity.
I hasten to add that I am not a 'self-sufficient' person who grows my own vegetables, rears my own animals and shuns anything packaged. It just doesn't fit in with my lifestyle. But I do worry about what I might be doing to my children's health without even being aware of it.
sermon over now 