Ah spring. Ah choo. For some 40 million people in the U.S. with seasonal allergies, the change in the weather brings sneezing, itching, coughing and general misery. But if it seems like there are more people dealing with allergies than there used to be, it’s not your imagination. Studies have shown that all sorts of allergies around the world have been on the rise since the 1980s. It’s not only environmental allergies and asthma, although the increase in those came first, for unknown reasons. More recently, there’s been a spike in food allergies, particularly in kids, with peanuts being the most infamous. Add food and skin allergies into the mix and you’re talking one in five Americans – some 60 million of us, according to the Asthma and Allergy Foundation of America. So what’s going on?
Allergies are very complex conditions, so the picture is far from clear, but there are some intriguing theories as well as basic facts.
Allergies are an overreaction of the immune system to an irritant – an allergen. When we’re born, we have a general immunity; we are in what’s called Th2 mode. As we grow, we switch into Th1 mode, during which our bodies acquire defenses against potentially harmful microorganisms. For many people, the development of our immune system goes swimmingly. We can fight off the effects of pollen or insect bites or peanuts with few problems.
For others, particularly those born with a genetic predisposition to allergies, the immune system jumps into warp speed. The sneezing, coughing, wheezing and watery eyes are all a hypersensitivity to dander, pollen or other elements in our environments. All of that’s miserable enough. But some people, typically children, face a more dangerous situation. Insect stings and food allergies can cause anaphylaxis, which is a potential death threat. The whole body reacts to the stimulus, and in the worst cases, the airways tighten and prevent breathing. Without quick treatment, people can die.
Some people point to better reporting of allergies as responsible for the bigger numbers, but it’s not a huge leap in logic to think that increased air pollution or the way we grow food now might have something to do with it. But a landmark study of environmental factors showed that something different might be going on.
From 1991 until 2000, experts followed the allergy and asthma incidence of nearly 32,000 children in East and West Germany. East Germany had a lot of heavy industry and not much in the way of pollution control. So you’d think those kids might have had the most allergies, right? No – it was the West Germans kids, even though they were living in a cleaner environment. The experts hypothesized that it was the lack of exposure to allergens that might be at the root of this unexpected result – that the West German kids weren’t around enough microbes and particles to kick their immune systems into the right gear.
Then, in 2013, a CDC report showed that food allergies in children increased by about 50 percent between 1997 and 2011. Today that means one in every 13 kids under 18. The increase in a serious allergy to peanuts, which tends to happen to those at a higher socioeconomic level, has perhaps been the most alarming.
Is it something in the peanuts today – something that is sprayed on them or genetic modification? Again, there’s no clear answer, but there is a theory that calls to mind the German study about environmental allergies. It’s called the hygiene hypothesis.
Basically, it posits that we may have become too clean and careful for our own good. If children aren’t exposed to potential food allergens, it may suppress the natural development of the immune system, in the same way as avoiding environmental elements does. That’s the theory. There’s also evidence that a rural lifestyle, where mothers and children tend to be around farm animals that carry all sorts of bugs and dirt, stimulates the proper immune-building response. Is it possible that all the wiping down with antibacterial cleansers and careful choices of food have gone too far?
Not so fast, though. On the other side of the debate, experts have noted that in Japan, which sets very high standards of cleanliness and is a largely urban society, there has been no rise in asthma. And kids who live in very poor housing in the US, which may be dirty from lack of maintenance, do have higher rates of asthma.
The theories are fascinating but don’t give us much clarity. It may be that we will never fully understand cause and effect when it comes to allergies. Recent exposure therapy in which children are given minute amounts of peanuts have shown promising results in desensitizing them, but most of us will have to continue to treat the symptoms of our allergies, not the cause. Gesundheit.
Sources:
Krämer, U. et al. (February, 2010). Differences in allergy trends between East and West Germany and possible explanations. Clin Exp Allergy, 40(2): 289-298. http://www.ncbi.nlm.nih.gov/pubmed/20210807
Romagnani, S. (July, 2004). The increased prevalence of allergy and the hygiene hypothesis: missing immune deviation, reduced immune suppression, or both? Immunology, 112(3): 352-363. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1782506/
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