Scientist are discovering that asthma is caused by candida or fungal overgrowth in the body. Once the candida or fungus becomes overgrown in the lungs asthma begins. All inhaled corticosteroids are known to cause fungal overgrowth in the mouth (thrush). If these inhalers cause thrush then it is my belief that they would also cause more fungal overgrowth in the lungs of asthma patients, and over time as the fungal/candida population gets bigger and bigger the inhalers become less effective.