We are in the midst of an allergy explosion. An estimated 30 percent of Americans, or roughly 100 million people, suffer from allergy and asthma; a Gallup study puts the figure at 50 percent. Globally, allergy affects 20 to 40 percent of the population. The rate in urban environments has increased for the past half century. In the United Kingdom, it''s estimated that up to half of all kids suffer from some allergic condition. Once upon a time, you knew a few people with allergies, maybe more than that if your family or neighbors were genetically unlucky enough to have a disposition (more on the genetics of allergy in chapter 2). Now? Probably you know, or know of, five to ten times that number. While many are born wired for their allergic condition, it may be that the environments we now inhabit, both outdoor and in, the behaviors we engage in, the products we use, and the foods we consume have all changed enough in a short time that we are confronted by a genuinely new reality.
The uptick has occurred not just in one or two kinds of allergy. It spans the spectrum. It''s seen in seasonal allergies and allergic respiratory disease, including asthma. Between 2001 and 2009, the number of Americans diagnosed with asthma grew by over 5 million, across all demographics. It''s seen in food allergies. The CDC says that food allergy in children rose by half again, between 1997 and 2011. The rate of peanut allergy doubled in the last decade. The European Academy of Allergy and Clinical Immunology reported a 700 percent rise over the last decade in allergic reactions among European kids.
Why is this happening? In many cases, allergy "triggers"--the source of the scourge, exposure to which sets off an immune system reaction ranging from unpleasant to activity-limiting to debilitating to deadly--have gotten bigger, badder, and way more prevalent. Ragweed, the central culprit behind fall hay fever for those residing in regions with seasonal climates, is growing faster and bigger in many places, and blooming longer, with more pollen per plant and possibly more potent allergic potential. Combine this with other environmental troubles, such as human-generated air pollutants, and it creates a potential synergistic, amplified impact on your health. Poison ivy today can be found more widely, and it''s generally bigger and more potent, too. Even our mix of trees has altered the (allergy) landscape. In 1950, the native American elm, once the most popular "street tree" in neighborhoods across the United States and other countries, was a modest shedder of insect-transported pollen. But then Dutch elm disease ravaged the elm population, killing off billions--yes, billions --of these trees in the 1960s and ''70s. Among their replacements were hardwood species like London plane sycamore and Norway maple, and a greater proportion of male trees, selected largely because they shed less, making it easier to keep streets, sidewalks, and yards clean--but they also produced more allergenic, wind-conveyed pollen.
Says renowned horticulturist and author Tom Ogren, "In many areas today, tree pollen makes up more than 70 percent of the total urban pollen load." Wasps, whose stings can cause allergic reaction ranging from swelling of the skin to hives to potentially deadly anaphylaxis, arrive earlier in the season and stay later. Fire ants, mostly a fixture in the South, seem over the past decade and a half to be moving gradually north and west. The mostly tropical triatoma, commonly called the kissing bug, is spreading northward. Mosquitoes are more prevalent in many areas, and their incubation time in certain regions has grown shorter. Of course, mosquitoes can cause harm far greater than allergic itching and swelling, such as West Nile virus, chikungunya, dengue fever, and the confounding, often devastating Zika, the last three of which are on the rise. Forests are flourishing in the eastern United States--good news, right?--but that contributes to an increase in the deer population, thus an increase in deer ticks and cases of Lyme disease. In the last fifteen years, the number of annual Lyme cases in Canada has increased from roughly forty to seven hundred; two decades ago, ticks lived and reproduced in two areas in Canada, today in thirteen.
The Lone Star tick, whose name bespeaks a southwestern habitat, is spreading north and east; its bite may trigger allergy to red meat, a particularly elusive condition to identify. The reason behind much of what I''ve just chronicled is mostly climate change, or increases in extreme weather." But climate change is hardly the only cause of the rise in allergy frequency, severity, and complexity. There are new threats in the air and water; in our food, homes, and offices; and on our bodies--our own "microenvironments"--that simply did not exist twenty or so years ago. These factors combine to make diagnosis more complicated. For example, people exposed to ozone plus ragweed allergen likely experience greater illness than those exposed to only one of the two--and it''s less simple to get at the root, or roots, of what''s going on. Our natural balance--by which I mean nature itself and our own individual nature--has been altered. When that happens, we may become overloaded, and an overreaction by the immune system becomes much more possible.
A study by Quest Diagnostics shows that our rate of sensitization to common allergens--really, the first step in becoming allergic--has increased. The range of increase in allergy is broad. So are the causes for the surge.