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» reasons for asthma

  • Causes of Asthma
    By Health Blog on May 3, 2010 | 2 Comments2 Comments  Comments

    The development of asthma appears to involve the interplay between host factors (particularly genetics) and environmental exposures that occur at a crucial time in the development of the immune system. A definitive cause of the inflammatory process leading to asthma has not yet been established. But some of the following are the most common causes of asthma.

    Innate immunity: Numerous factors may affect the balance between Th1-type and Th2- type cytokine responses in early life and increase the likelihood that the immune response will down regulate the Th1 immune response that fights infection and instead will be dominated by Th2 cells, leading to the expression of allergic diseases and asthma. This infects early in life, exposure to other children (e.g. presence of older siblings and early enrollment in child care, which have greater likelihood of exposure to respiratory infection), less frequent use of antibiotics, and “country living” is associated with a Th1 response and lower incidence of asthma, whereas the absence of these factors is associated with a persistent Th2 response and higher rates of asthma. Interventions to prevent the onset of this process (e.g. with probiotics) are under study, but no recommendations can yet be made.



    Genetics: Asthma has an inheritable component, but the genetics involved remain complex. As the linkage of genetic factors to different asthma phenotypes becomes clearer, treatment approaches may become directed to specific patient phenotypes and genotypes.

    Environmental factors: Two major factors are the most important in the development, persistence and possibly the severity of asthma: airborne allergens (particularly sensitization and exposure to house-dust mite and Alternaria) and viral respiratory infections (including respiratory syncytial virus [RSV] and rhinovirus).

    Other environmental factors are under study: Tobacco smoke (exposure in utero is associated with an increased risk of wheezing, but it is not certain this is linked to subsequent development of asthma), air pollution (ozone and particular matter) and diet (obesity or low intake of antioxidants and omega-3 fatty acids).The association of these factors with the onset of asthma has not been clearly defined. A number of clinical trials have investigated dietary and environmental manipulations, but these trials have not been sufficiently long term or conclusive to permit recommendations.

    Implications for Treatment

    Knowledge of the importance of inflammation to the central features of asthma continues to expand and underscores inflammation as a primary target of treatment. Studies indicate that current therapeutic approaches are effective in controlling symptoms, reducing airflow limitation and preventing exacerbations, but currently available treatments do not appear to prevent the progression of asthma in children. As various phenotypes of asthma are defined and inflammatory and genetic factors become more apparent, new therapeutic approaches may be developed that will allow even greater specificity to tailor treatment to the individual patient’s needs and circumstances.

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