Asthma - pathology and phytotherapeutic applications
Asthma is certainly not a new disease, with descriptions of its pathogenesis and treatment dating back to Hippocrates and Paracelsus (Floyer, 1698, pA6). Towards the end of the 20th century and into the 21st the prevalence of asthma has increased in the developed world (Holgate and Frew, 2002, p874; Moxham and Costello, 2002, p652).
Once classified as ‘extrinsic’ asthma for those types with a known cause such as dust mites; and intrinsic asthma for types with no known cause, these terms have now come to an end. It is now widely accepted that asthma is a chronic inflammatory disease of the lungs and approximately half of all asthma cases have an allergic component to them (Holgate and Frew, 2002, p874).
Occupational asthma is considered to play an important role in late-onset asthma. However, it appears that many of these cases give a childhood history of respiratory symptoms in keeping with asthma (Holgate and Frew, 2002, p874). Although the strongest predictor of childhood asthma risk is a family history of asthma, particularly from the mother (p=<0.001: Darlow et al, 2000, p292; Ball et al, 2000, p540), the increased prevalence of asthma is believed to be more likely due to environmental factors than a genetic shift (Holt, 1995, p44). It has been found that another strong predictor is maternal smoking in pregnancy (p= < 0.005; Darlow et al, 2000, p292). Certainly smoking during pregnancy is associated with increased cord blood IgE levels (Landau, 1995, p30-31). A family history of atopy also shows strong associations (Darlow et al, 2000, p292).