“Microbiome” and Allergies

Explained By Allergists McLean VA Patients Trust
There has been an increase in the incidence of allergic diseases over the past 20-30 years and this phenomenon is more pronounced in industrialized countries compared to developing countries.  Many researchers believe that environmental and dietary changes play major roles in the development of allergies.  This is true in areas such as Falls Church, VA, Gainesville, VA, and Tysons Corner, VA as well as the rest of the Washington, DC metro area.

The primary role of our immune system is to defend and protect us from infections caused by germs like viruses, bacteria, and parasites.  Exposure of the immune system to infections with germs in early life stimulates the maturation of the immune system in a normal balanced way.  The absence of this stimulation can trigger the immune system to mistake innocuous substances such as dust mites, molds, pollens, and certain foods as potentially harmful and mount a defensive attack on them causing allergic disease.  This “hygiene hypothesis” aims to explain why more people suffer from allergic disorders in the developed, overly hygienic Western world.  An alternative interpretation of the evidence supporting the hygiene hypothesis forms the basis for the “microflora hypothesis,” which says that rather than specifically limiting infection, even the decreased exposure to microbes changes the colonization of bacteria of the infant gut, which has a negative effect in the development of the normal immune system which ultimately leads to allergic disease.

An adult human harbors about 100 billion bacteria in the intestines alone.  These gut bacteria account for 90% of the cells in the human body!  Human cells contain about 21,000 different genes, but the microbes living in the human comprise about 3 million genes.  The composition and function of the bacteria in the gut varies from person to person (i.e., biodiversity) and evolve during the first years of life and stabilize within the first 3 years of life.

The development of the gut microbiome (i.e., all the microorganisms that live in the gut) is influenced by interactions between diet, environment, and host-associated factors.  There is increasing evidence that these bacteria play many helpful roles in the modulation of our immune responses, especially in maintaining a balance between 2 different types of white blood cells called Th1 lymphocytes and Th2 lymphocytes.  The Th1 lymphocytes help protect us from infections, whereas the Th2 lymphocytes help mediate allergic disease.

The emerging hypothesis infers that environment or lifestyle-driven aberrancies in the early-life gut microbial composition and function represent a key mediator of childhood allergies and asthma.  Significant perturbations in the gut bacterial composition, especially reduced diversity, in the Western societies due to frequent antibiotic usage, environmental and lifestyle changes, etc. have disrupted the mechanisms of mucosal tolerance leading to more allergic disease.

Epidemiologic and clinical data supporting this interpretation include:

  1. A positive correlation between increasing risk for asthma and allergies and increasing use of antibiotics in industrialized countries.
  2. Correlations between altered fecal microbial flora and atopic disease
  3. Successful prevention and/or reduction of allergies in some individuals by the use of oral probiotics (live commensal bacteria) and dietary changes.

A recent meta-analysis of 25 studies revealed that the administration of probiotics reduces allergy-causing IgE antibody levels and the risk of atopic sensitization.  An example of dietary factors influencing allergies is the landmark LEAP study which demonstrated that early introduction of peanut products to high risk infants significantly decreased the subsequent development of peanut allergy.

There are a number of ongoing studies which will improve our understanding of the mechanisms underlying allergic disorders and hopefully offer new and exciting options in the management of these conditions in near future.

The board certified allergists of Black & Kletz Allergy always strive to keep abreast of new developments in the field of Allergy, Asthma, and Immunology in order to offer new and emerging diagnostic and therapeutic modalities, as soon as they are available.  Black & Kletz Allergy has 3 offices in the Washington, DC, Northern Virginia, and Maryland metropolitan area.  We have offices in Washington, DC, McLean, VA (Tysons Corner, VA), and Manassas, VA and offer on-site parking at each location.  In addition, the Washington, DC and McLean offices are Metro accessible.  There is a free shuttle that runs between the McLean office and the Spring Hill metro station on the silver line.  The allergy specialists of Black & Kletz Allergy see both adults and children in the Tysons Corner, VA, Falls Church, VA, and Gainesville, VA areas and we have been serving the greater Washington metro area for over 50 years.  Please call one of our convenient offices to make an appointment or alternatively, you can click Request an Appointment and we will reply within 24 hours by the next business day.