Seasonal Allergies Could Alter Your Brain

A recent study warns seasonal allergies, commonly called hay fever, could give you more than just stuffy nose and itchy eyes; it could also change your brain. The study published in the open-access journal Frontiers in Cellular Neuroscience confirms from brains of mice exposed to allergen.

From the use of a model of grass pollen allergy, the scientists found that the brains of mice exposed to allergen actually produced more neurons in the hippocampus, the part of the brain responsible for forming neurons, than controls. What marvels the research team was how allergies could possibly affect memory, when the same reaction deactivated microglia, the immune cells of the brain.

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Barbara Klein, from the University of Salzburg in Austria, also one of the authors of the study, explains:

 “It was highly unexpected to see the deactivation of microglia in the hippocampus, partly because other studies have shown the reverse effect on microglia following bacterial infection.”

For the study, scientists had two groups of lab mice exposed to an allergen, one as allergy models and others as controls. The researchers put forward series of theories to explain the reason for the unexpected deactivation of the microglia in the hippocampus of allergic mice i.e. it might only be a regulatory mechanism meant to protect the hippocampus.

The research team however speculated that the increase in hippocampus neurons may also have some consequences on long-term learning and memory.

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A report by World Health Organisation (WHO), had it that, 10-30 per cent of the population worldwide suffers from allergic rhinitis, commonly called hay fever.

 “We know that the response of immune system in the body is different in case of an allergic reaction vs a bacterial infection, added Klein. What this tells us is that the effect on the brain depends on type of immune reaction in the body.”


Barbara Klein, Heike Mrowetz, Josef Thalhamer, Sandra Scheiblhofer, Richard Weiss, Ludwig Aigner. Allergy Enhances Neurogenesis and Modulates Microglial Activation in the Hippocampus. Frontiers in Cellular Neuroscience. 2016

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