Allergies were quite rare in the early 1900’s, but now they are quite common. It is estimated that 20-25% off the US population is affected by environmental
allergies. Asthma and food allergies are now more common than ever. In fact, over the past several decades, the frequencies of asthma and peanut allergies
have doubled.
No one knows for sure why allergies are becoming more common. One possible explanation is that it is related to our clean environment. When we
compare the frequency of allergies in different parts of the world, we see that allergies are much more common in industrialized areas such as the United States
and Europe compared to developing areas such as Africa. Within the United States, we see that the frequency of allergies is higher in suburban communities
compared to rural, farming areas. The common threat to all of these is that the cleaner the environment, the more likely it is that allergies will develop (called
the hygiene hypothesis). With a cleaner environment there are fewer exposures to bacteria, viral, and parasitic infections. This causes a change in our immune
system’s processes so that it is more primed for allergies.
allergies. Asthma and food allergies are now more common than ever. In fact, over the past several decades, the frequencies of asthma and peanut allergies
have doubled.
No one knows for sure why allergies are becoming more common. One possible explanation is that it is related to our clean environment. When we
compare the frequency of allergies in different parts of the world, we see that allergies are much more common in industrialized areas such as the United States
and Europe compared to developing areas such as Africa. Within the United States, we see that the frequency of allergies is higher in suburban communities
compared to rural, farming areas. The common threat to all of these is that the cleaner the environment, the more likely it is that allergies will develop (called
the hygiene hypothesis). With a cleaner environment there are fewer exposures to bacteria, viral, and parasitic infections. This causes a change in our immune
system’s processes so that it is more primed for allergies.
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Why are allergies more common now than they used to be?
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