Everyone thinks they know what an allergic reaction looks like: red, itchy eyes and a runny nose that erupts within 20 minutes of entering a house with a cat; a scratchy mouth and throat after eating raw carrots; hives after taking a medicine. Allergies can be triggered by anything from birch pollen to pet dander, peanuts to penicillin, and more than 50 million people in the U.S. suffer from seasonal, indoor/outdoor, food, skin, and drug allergies every year.
As you’ll recall, an allergic reaction is an immune response in which the immune system mistakes a normally harmless antigen, such as a dust particle, as a threat and produces large numbers of IgE antibodies to combat it. When the immune system comes into contact with that antigen again, the IgE antibodies are ready and waiting to mount an attack, releasing histamines and other inflammatory molecules that can result in itchy or swollen eyes, drippy nose, asthma, rashes, and a host of other physical symptoms.
Food allergies are particularly common—it’s estimated that 5.6 million children in America have them (that’s about 8% or 1 in 13 kids). Eight foods are responsible for about 90% of food allergy reactions: milk, eggs, wheat, soy, tree nuts, peanuts, fish, and shellfish—with milk, eggs, and peanuts being the most common. However, just about any food can cause an allergic reaction.
And as it turns out, everyone doesn’t actually know what an allergic reaction looks like. In fact, some allergies don’t manifest with physical symptoms at all.
How allergic reactions can manifest mentally.
We know that sometimes symptoms that appear neuropsychiatric, like depression, are in fact a result of inflammation. Since an allergic reaction is actually an inflammatory response, we shouldn’t be surprised that multiple studies have found a connection between allergies and psychiatric disorders. One population-based study found that people with allergies had a higher risk of developing depression, anxiety, or bipolar disorder than those without.
Cow’s milk has been shown to trigger increased behavioral and emotional disturbances in mice sensitized to dairy, and doctors have seen positive results from elimination diets in patients suffering from treatment-resistant depression, indicating that the covert reaction to certain foods may have been contributing to a resistance to their medications.
Consistently, elevated levels of IL-6 are found in people suffering from major depression and anxiety. IL-6 is one of the inflammatory cytokines responsible for loosening the tight junctions of the intestinal wall, allowing inflammatory molecules into the circulation, where they can then travel to the brain (see the gut-brain-immune axis). It can be produced in response to some medications, stress, infections—and allergies.
Potential reasons childhood allergies are on the rise.
According to the CDC, the number of children with food allergies rose 50% between 1997 and 2011, and the rates continue to rise. No one is really sure why, and the research on how to prevent allergies continues to evolve. Here are some ideas:
1. Kids weren’t exposed to allergenic foods early enough.
For a time, the best strategy seemed to be for parents to avoid introducing allergens into their infants’ diets, but recent studies suggest the opposite is true, and that offering allergenic foods to healthy infants can have protective effects.
2. Environmental factors compromised kids’ immune systems.
Others postulate that the rise in childhood allergies may be due in part to our overreliance on antibacterial hygiene products that don’t allow the body sufficient exposure to microbes or parasites; antibiotic use; obesity; vitamin D deficiency; and environmental factors such as chemicals, pollution, and heavy metals that compromise the immune system.
But the theory that’s currently garnering the most support is that the rise in allergies could correspond to the rise in the incidence of intestinal hyperpermeability, or leaky gut. Many of the above physical and environmental factors, as well as stress, can contribute to this condition.
It remains unclear whether it’s the leaky gut allowing large proteins to enter the circulation that triggers the allergic immune response or the allergic reactions themselves that loosen the tight junctions of the gut lining. Regardless, researchers and my own observations confirm that loss of the integrity of the intestinal lining plays an important role in susceptibility to food allergies.
From the book BRAIN INFLAMED by Kenneth A. Bock, M.D. Copyright © 2021 by Kenneth A. Bock, M.D. Reprinted courtesy of Harper Wave, an imprint of HarperCollins Publishers.