Hygiene Hypothesis

It has been observed that children who live on farms or in rural areas, who belong to families with three or more siblings, and who grow up in less-developed countries often have a lower incidence of allergies than other children. This rising phenomenon has been labeled the “hygiene hypothesis.”

allergy family

The hygiene hypothesis proposes that exposure to allergens in the environment during a person’s early years in life minimizes the risk of developing allergies by boosting the immune system’s activity. In contrast, people who live in clean environments in early life and who lack exposure to infectious agents, symbiotic organisms, and parasites during childhood are susceptible to allergic diseases. The lack of exposure is thought to be connected to delayed development of immune tolerance.

The validity of the hygiene hypothesis is supported by clinical trials and experimental models. For example, researchers at Brigham and Women’s Hospital conducted a study on the immune system of mice living in areas that were low on bacteria and other microbes and compared them to mice living in a normal environment that contained microbes. They discovered that germ-free mice had enlarged lung and colon inflammation that resembled asthma and colitis respectively. Most importantly, the researchers found that exposing the germ-free mice to bacteria during their first weeks of life led to a normalized immune system and disease prevention. Moreover, early-life exposure to microbes provided long-lasting protection as predicted by the hygiene hypothesis.

The hygiene hypothesis, however, cannot fully explain the reason behind higher rates of allergic asthma among poor African Americans located in inner city areas. Further studies are being conducted in order to understand the role different environments play in the development of allergy.

About The Author

Stuart H. Agren, M.D.

Stuart H. Agren, M.D. completed his undergraduate studies at the University of Utah and went on to earn his Doctor of Medicine from Tulane University School of Medicine in 1974. He completed additional training at L.D.S. Hospital in Salt Lake City, Utah and then established his private medical practice starting in 1975. Dr. Agren completed a mini-residency in Industrial Medicine at the Robert Johnson School of Medicine at Rutgers University and also completed training to become a certified Medical Review Officer.

Dr. Agren was the Medical Director at TRW and McDonnell Douglas in Mesa, Arizona and at Stauffer Chemical and Kennecott Copper in Salt Lake City, Utah. He also served as an adjunct faculty member at Arizona State University.

In his private medical practice, Dr. Agren specialized in family practice and allergy. In his work as a private practice allergist, he was one of the first doctors in the country to prescribe sublingual immunotherapy to his patients as an alternative to subcutaneous immunotherapy (allergy shots). He has also been a trailblazer in the field of food allergy treatment and research, developing a program to treat multiple food allergies simultaneously using sublingual immunotherapy. Dr. Agren has been featured on local CBS, NBC, and ABC news affiliates and won the peer-nominated “Top Doc” award from Phoenix Magazine.

After 20 years in private practice, Dr. Agren became the Founder and President of AllergyEasy, which helps primary care physicians around the country offer allergy testing and sublingual immunotherapy treatment to their patients. Over 200 physicians in over 32 states use the AllergyEasy program to help their patients overcome environmental and food allergies and asthma.