Seasonal allergies may change brain, but scientists unsure how

SALZBURG, Austria, Aug. 8 (UPI) -- During allergic reaction scientists found the brain produces more neurons, formed in the hippocampus, but deactivates microglia, the brain's immune cells -- a reaction they say they do not understand, either the cause or the effect.

Season allergic rhinitis, more commonly known as hay fever, develops in response to something in the environment, such as mold spores or pollen, causing symptoms from a runny nose and itchy face to congestion and fatigue, but the effects of induced allergic reaction on the brains of mice surprised researchers.

"It was highly unexpected to see the deactivation of microglia in the hippocampus," Barbara Klein, a researchers at Paracelsus Medical University in Austria, said in a press release. "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. What this tells us is that the effect on the brain depends on type of immune reaction in the body."

The findins were published in the journal Frontiers in Cellular Neuroscience.

Researchers hypothesize the reduced microglia expression produces some type of short-term protection for the hippocampus -- noting in the study they don't actually understand why it happens.

"Clearly, more experiments investigating the impact of different types of systemic inflammation on the central nervous system are needed to further the understanding about the interplay between peripheral immune activation and CNS functions," researchers wrote in the study.