October. This is one of the peculiarly dangerous months to speculate in stocks. The others are July, January, September, April, November, May, March, June, December, August, and February."
- Mark Twain, Pudd'nhead Wilso
Allergies are on the rise in most developed countries. And they are more common, not just something that happens when flowers pollinate in spring.
We are not yet sure why they are becoming more year-round or why people are most susceptible, but we have ideas. One suggestive (if somewhat controversial) idea is the hygiene hypothesis, where immune systems aren't challenged enough when young so they over-respond to stimuli later in life.
With respect to them being more year-round, it is important to realize that all months have always contained airborne allergens, even if they are different in different places and at different times of the year. At the same time, different people respond to different allergens, and with differing severities.
But there is reason to think climate change is playing a role here. Consider three factors:
- Warmer temperatures: Warmer temperatures are causing plants to bloom earlier and later in the year. This means that people with allergies may be exposed to pollen for longer periods of time.
- More extreme weather events: Extreme weather events, such as heat waves, droughts, and floods, can damage plants and make them more likely to produce pollen. This can also lead to an increase in mold growth, which can also trigger allergies.
- Changes in plant distribution: Climate change is causing some plants to move to new areas. This means that people who have never had allergies before may start to experience them as plants that they are allergic to move into their area.
We can now add to this troubling picture data from a new paper (based on Japanese data) on the broader consequences of allergens. The paper shows that pollen concentration, which affects cognition, thus feeding into everything from academic performance to adult daily life, leads to a higher incidence of traffic accidents with commensurate mortality.
See the following graph, which is striking:
While people try to get around their allergy symptoms in various ways, including spending on medication, and even avoiding going outdoors, allergies are likely going to grow in frequency and consequentiality. In other words, expect more Claritin sales in the future, as well as people being more observant of pollen counts, as well as more filtering of inside air. But the allergy side of modern life is changing, and we are only beginning to understand the broader consequences.
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