Epidemiological studies have revealed an association between pollution and allergic respiratory diseases. The main pollutants in this sense are nitric oxide, ozone, and particulate matter. The present review on one hand addresses the chemical characteristics of each of these three groups of pollutants and their main sources, and on the other examines their effects upon allergic respiratory diseases--placing special emphasis on the effects of diesel exhaust particles. For each of the pollutants, the underlying mechanisms capable of influencing allergic respiratory diseases are commented. Lastly, an evaluation is made of some of the genetic aspects related to the response to pollutants.