More than just itchy eyes and a stuffy nose.
Based on new findings from a study with mice, researchers from the University of Salzburg, Paracelsus Medical University, and the Paris Lodron University of Salzburg, Austria have found that seasonal allergies may actually change the brain.
The team decided to focus on the hippocampus, which is the brain region involved in forming new memories. It’s also the area where neurons continue to be formed throughout life, and using a model of grass pollen allergy, the researchers found that allergen-exposed mice produced more neurons than controls.
Since the team saw an increase in new neurons in the hippocampus during an allergic reaction, they wondered what the consequences of allergies would be on memory. To explore this, they observed the microglia, which are the brain’s immune cells that are linked to the formation and functioning of neurons.
The scientists were surprised to find that the allergic reaction deactivated the microglia in the brains of mice. While allergies kickstart the body’s immune system, they seem to have the opposite effect on the immune cells of the brain.
"It was highly unexpected to see the deactivation of microglia in the hippocampus," one of the study authors Barbara Klein said in a press statement. "Partly because other studies have shown the reverse effect on microglia following bacterial infection.”
"We know that the response of immune system in the body is different in case of an allergic reaction vs a bacterial infection,” she continued. “What this tells us is that the effect on the brain depends on type of immune reaction in the body."
Another interesting finding from the study, which appears in the journal Frontiers in Cellular Neuroscience, is that allergic reactions also cause an increase in neurogenesis — the process in which nervous tissue is grown and developed, which is known to decline with age.
With these new insights in mind, the researchers are curious to find out whether brain aging in allergy-prone individuals would progress differently than those without allergies.
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