For nearly 100 years it has been known that asthma is a condition in
which an acute respiratory response may follow inhalation of some material
to which a person is sensitized. The list of such materials grew slowly over
50 years (it started with horse dandruff), continued with ragweed and grasses,
and on the basis of skin responses, was believed to include a wide variety
of foodstuffs (including nuts).1 Domestic pets,
and later, pests such as cockroaches and house dust mites came to the fore,
and as occupational asthma came to be recognized, the list expanded still
further. However, the focus of such awareness has been on agents that directly
cause allergic reaction, and therefore can be diagnosed via skin tests, rather
than on agents that cause nonspecific generalized inflammation, such as air
pollution.