After years of inhalers and decongestant prescriptions, the cause of your allergies may not be the pollen in the air after all, but the contents of your gut.

Angela Cesere
A microscopic view of pollen grains carried on the body of a wasp. Two University professors are researching the link between the use of antibiotics and the rise in allergies. (Courtesy of University of Cape Town)

Antibiotics can cause changes in the human digestive system that, coupled with an unhealthy diet, could be responsible for recent increases in the development of allergies and asthma, according to research findings released Dec. 23 from the University Medical Research Center.

“Antibiotics are great. They are, but there is a price to pay, and that’s what we have ignored”, said Gary Huffnagle, a professor of internal medicine, microbiology and immunology. Huffnagle, the head researcher on the project, and Mairi Noverr, a University postdoctoral fellow, developed a study to test their hypothesis that antibiotics change the microflora lining — a mixture of fungus and bacteria in the gastrointestinal tract or the system of organs that digests food. According to their research findings, this change disrupts the immune system and its ability to ignore inhaled allergens.

Noverr exposed the laboratory mice to a broad-spectrum antibiotic, which kills a wide range of bacteria, for five days to kill their gut bacteria. Then, to help the mice quickly redevelop a bacterial mix in their GI tract, they were exposed to Candida albicans, a type of yeast normally found in the GI tract. Two days later, the mice were exposed to ovalbumin, an experimental allergen known to illicit an allergic response. Comparing the mice that received the antibiotics to those that did not, Noverr found that the mice treated with the antibiotic were much more sensitive to the allergen.

Now that they have found a correlation between the GI tract the immune system, Huffnagle and Noverr want to determine how the gut microflora communicates with the immune system.

Noverr said that special cells called regulatory T cells, which are generated in the GI tract, help to maintain tolerance to allergies. Huffnagle and Noverr believe these cells can travel to other mucosal surfaces, such as the lungs, where they can dampen immune response. They plan to investigate whether or not changes in microflora influence the development of regulatory T cells.

Their current results confirm their hypothesis that the increase in allergies, asthma, and many other diseases over the last 40 years in Western industrialized societies can be credited to the widespread use of antibiotics, Huffnagle said.

Noverr said they are interested next in studying the effect of environmental factors, particularly the effects of various diets on microflora and allergies. Scientists have suggested that the “western diet,” which is high in processed fat and sugar is responsible for a number of health problems. They hypothesized that today’s modern diet does not provide the body with appropriate nutrients to maintain a healthy mix of microflora in the GI tract.

Huffnagle said he hopes that antibiotic prescriptions will eventually be accompanied by supplemental dietary instructions after the medication’s use ends, to help rebuild a healthy mix of microflora.

Such a diet should be high in raw fruits and vegetables, he explained, since other laboratory results have shown that plants produce dietary antioxidants the human body needs to fight infection. These antioxidants, concentrated primarily in the rind or skin of fruits and vegetables, could help to restore the normal mix of gut microflora.

Results of the study, as well as a multitude of anecdotal evidence also suggest that many people who have developed allergies may be able to alleviate their allergy symptoms simply by making dietary changes, Huffnagle said

And, Huffnagle and Noverr succeed in determining how microflora in the GI tract communicates with the immune system, treatment or prevention of allergies and inflammatory diseases may become a reality.

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