By Henry Ehrlich
A couple of weeks ago, a West Coast neuroscientist named Jessica Martin, who blogs as foodallergysleuth, asked me my thoughts on the term “hygiene hypothesis” as an explanation of for the growing problem of allergic disease. She is a young mother and her child has food allergies. I find HH inadequate in casual conversation because for one thing it is limited by how people respond to the word hygiene, which to some raises questions about their hand washing, others to their housekeeping, to others about living in cities vs. the suburbs, or the suburbs vs. a farm. What hygiene means to a researcher is probably more complex than what it means to an ordinary person trying to make sense out of a child’s health. (For a comprehensive discussion of the multiple contributors to allergies, see Do Allergies Develop in the Womb? by Michelle North, PhD and Anne Ellis, MD.)
The short answer for me is to refer to the work of Dr. Susan Prescott whose book The Allergy Epidemic I reviewed two years ago. Her explanation is that changes in our environment and diet have done bad things to the parts of the body that are exposed to them: “As allergic reactions are directed to the external environment, it makes sense that the areas of the body affected are those that are in most immediate contact with the environment: the skin, the airways and the gut.” The changes, moreover, are cumulative as changes in the way our genes function, called “gene expression”, not only alter who we become in our lifetimes, but are passed from generation to generation.
In a new article in the Journal of Allergy and Clinical Immunology, Dr. Prescott elaborates on her thesis to encompass a “global pandemic” of diseases of which allergies and asthma are an important, if under-appreciated, part. The underlying problem is chronic low-grade inflammation. Let’s not forget, the presence of inflammation is generally a sign that the immune system is responding to something that wants to harm us. When you’re running a fever, for example, you are trying to fight a virus or a bacterial infection. On the other hand, if you have allergies, it’s responding to something that shouldn’t be a problem.
However, just because your lucky friends don’t have allergies doesn’t mean their immune systems aren’t reacting to the same environmental assault you are. In fact, your allergies may be doing for your neighbors and relatives what—using Dr. Chiaramonte’s favorite metaphor—the canary does for coal miners. Prescott writes in her article, “as the most common and earliest-onset NCD, the epidemic of allergic diseases points to specific vulnerability of the developing immune system to modern environmental change… The innate immune system provides a clear example of this convergence, with evidence that physical activity, nutrition, pollutants, and the microbiome all influence systemic inflammation through Toll-like receptor pathways (notably Toll-like receptor 4), with downstream effects on the risk of insulin resistance, obesity, cardiovascular risk, immune diseases, and even mood and behavior.”
Maybe those who give short shrift to the way our children sneeze, wheeze, hive, and suffocate will pay attention to diabetes, obesity and heart disease.
Prescott advocates an interdisciplinary, holistic approach to comprehending and identifying these disparate manifestations of inflammatory disease and then undertaking appropriate “lifestyle and environmental interventions” aimed at prevention, starting early in children’s lives.
Dr. Prescott also earmarks a special role for allergists: “As practicing allergists, we must embrace the challenge of more fully understanding the interaction between the environment and immunity. We have the opportunity to be the specialty that leads the way in advising families about the significance of the immune system for many aspects of health, including the limitations of our current understanding. Clinicians often ignore this, and people then seek less rigorous sources for advice. Even if the answers are not clear, we need to be educated so we can put this in context for patients.”
With imperatives like that, it should make us nervous that the numbers of clinical allergists are dwindling, both in the United States and Australia.
Prescott is asking a lot of us. She knows full well that behind the environmental changes that have inflamed us, however low grade the inflammation, lie the way we heat and the way we eat, among other things. She should take heart because in Australia, which has more allergies and asthma per capita than the U.S., change can happen. By coincidence, just about the same day Dr. Prescott’s article hit the web, Bloomberg reported:
RENEWABLE ENERGY NOW CHEAPER THAN NEW FOSSIL FUELS IN AUSTRALIA; Australia wind beats new coal in the world’s second-largest coal exporter
That’s a start.
(This website has covered many aspects of the larger issue, including gut bacteria, the protection farm life seems to afford the Amish, environmental exposures that lead to epigenetic changes, and the experimental use of hookworms to treat celiac disease.)