The general consensus among the medical profession is that children grow out of allergies and adults grow into them. On the whole the implication is therefore that children's allergic problems and food sensitivities get better whilst adults tend to get worse. I grew out of my hay fever in my teens and then developed insect sting allergy 25 years later.
Having said all that a large percentage of allergy suffers still lose their allergy spontaneously but if you are having anaphylactic responses do you really want to wait to find out?
Good to be back from my holiday for a few weeks - no Paris Hilton this year!
David