Asthma and related allergic disorders in childhood have increased considera
bly in prevalence over the last few decades. During the same period of incr
easing morbidity from childhood asthma in the community, there have been dr
amatic advances in understanding of the basic immunopathologic features of
the disease and consequently the development of a far more rational approac
h to its treatment. The immunopathologic condition of eosinophil-mediated a
irway inflammation is established very early in the evolution of asthma in
childhood. It may even antedate the onset of symptoms. The present state of
the art dictates that early intervention with potent therapies cannot be j
ustified on the basis of symptoms alone and may in any case have no influen
ce on the natural history of the condition, This means that current cautiou
s therapeutic guidelines should continue to be followed. However, with the
development of more accurate markers predicting ongoing disease, it will be
possible to evaluate a whole range of early interventions in the future. M
uch evidence, though indirect, points to the possibility that the only true
prophylaxis that will affect the natural history of asthma will need to be
commenced before clinical features are manifest.