ABSTRACT
Health effects resembling respiratory sensitization (allergy) have been recognized for well over 2000 years but recently the condition, known as asthma, has become more prevalent, in particular, in affl uent countries, and has been identifi ed as the cause of debilitating and potentially fatal disease. Allergy may be defi ned as the adverse health effects resulting from a specifi c immune response. More specifi cally, chemical respiratory allergy can be defi ned as the adverse health effects that result from the stimulation by chemicals, drugs, or proteins of specifi c immune responses (Kimber and Dearman, 1997). Such responses tend to occur only in a minority of individuals after exposure to a substance to which they have become sensitized. Furthermore, the adverse effects occur at exposure levels well below those that would have induced effects previously in the same individuals or would be expected to occur as a result of nonimmunologically mediated mechanisms, such as irritation.
