An article in Nature Medicine in March of 2012 showed that changes in the commensal microbes in the gut or antibiotic treatment predispose people to systemic allergic diseases. The role of the basophil white blood cell in this process was found to be related to heightened allergic responses in the lung and to elevated levels of IgE antibodies.
We know from previous studies that the normal commensal organisms in the gut act as sentinels that communicate with immune cells of the gut via cytokine messengers. When dangerous microbes enter the gut these sentinels send cytokine messages to the immune cells of the gut that make up at least 2/3 of the entire immune system, to make antibodies. However, when normally inert substances such as pollen enters the gut, it sends messages instructing the immune system to relax.