Mouth breathing worsens lung function in mild asthmatics
Recent research show that, switching from nose to mouth breathing causes a reduction in lung function among normally asymptomatic patients with mild asthma. The adverse effect of mouth breathing is well known in symptomatic asthmatics and contributes to exercise- induced asthma attacks. Nose breathing is protective against exercise-related symptoms. Bypassing the filtering effects of nasal breathing allows more aeroallergens to reach the lungs and causes drying and cooling of bronchial mucosal surfaces, say Hallani et al. After 1 hour of enforced mouth breathing, eight women with mild, asymptomatic asthma had about a 5% reduction in FEV1. They also reported slight breathing difficulties after the experiment, and three participants suffered coughing and/or wheezing.They add: “The combination of symptoms in association with a 5% reduction in FEV1 values suggests that this is a clinically important difference in FEV1.”When the women breathed only through their noses for 1 hour, their lung function was not affected, at 101.2% and 101.1% predicted before and after the experiment, respectively. Asthmatic patients switch from nose to mouth breathing at about half the nasal resistive threshold load of healthy people researchers note.

Respirology 2008; 13: 553–558

Maternal farm exposure can protect newborns from allergies
German researchers have found that babies born to mothers exposed to farms, particularly to barns and farm milk, while pregnant develop protection from allergies. Functional suppression was also more pronounced in offspring of farming mothers.“Early life exposure to a farming environment and in particular maternal exposure to farm milk and barns in pregnancy modulates T regulatory cell function in cord blood,” the authors commented. They concluded: “This may indicate a functional activation of T regulatory cells in neonates, potentially contributing to the allergy-protective effect in farming children.”
American Thoracic Society International Conference; Toronto, Ontario, Canada: 16–21 May 2008

Meta-analysis rejects dietary antioxidant link to asthma
In a meta-analysis it is has been found that low dietary intake of antioxidants is unlikely to account for the rising prevalence of asthma. The meta-analysis was based entirely on cross-sectional studies, but Jinming Gao (Peking Union Medical College Hospital, Beijing, China) and colleagues say their findings are consistent with the results of three prospective studies that failed to demonstrate a protective effect of vitamin C and E supplementation against asthma. Although this finding implies a role for vitamin C in preserving lung function, the team stresses that smoking and second-hand smoke exposure may affect the results by reducing both vitamin C levels and lung function.“The influence of a ‘good diet’ in preventing the development of asthma remains poorly understood and knowledge is limited,” Gao et al conclude. They note: “It remains possible that the current view of the importance of vitamins C and E is due to other associated nutrients and lifestyle exposures that are currently underrecognised.”
Respirology 2008; 13: 528–536

Smoking may reduce allergen tolerance
Cigarette smoke enhances acute allergic airway inflammation and delays tolerance to prolonged challenge with inhaled antigen in experimental asthma, Belgian researchers report in the journal Respiratory Research. Recently, Chris Van Hove and colleagues from Ghent University found that eosinophilic airway inflammation in allergic mice could be cleared by repeated allergen challenge, which resulted in a state of inhalational tolerance.
Respiratory Research 2008; 9: 42