Bacteria or fungi in the gastrointestinal (GI) tract play a major role in an individual's sensitivity to allergens. Michigan researchers found that changes in the normal mixture of microflora, bacteria, and fungi in the GI tract can build up the immune system's reaction to common allergens in the lung and raise the chance of developing chronic allergens or asthma. The common allergens include pollen and animal dander.
The researchers concluded that alterations in gut microflora as a result of widespread use of antibiotics plus a high-fat, high-sugar, low-fiber diet may be responsible for the major rise in incidences of chronic asthma and allergies in Western civilized countries. (The findings were reported in Infection and Immunity, January 2005.)