In a study published this week in Scientific Reports, scientists found that a single allergic reaction during pregnancy prompts sexual development changes in the brains of offspring that last a lifetime. Previous research had shown that insults to the immune system, including stress, infection, and malnutrition, can change brain development, but this new research highlights the important role allergies could play.
Female rats born to mothers exposed to an allergen during pregnancy acted more characteristically “male” and had nervous systems that looked more like those seen in males. These mice tended to mount other females and to be more interested in female bedding. The male offspring, on the other hand, showed a tendency toward more female characteristics and behaviors, though the changes were not as significant.
“The study shows for the first time that an allergic reaction in a mother could alter the sexual development of its offspring,” says senior Kathryn Lenz of Ohio State University. “This allergic response is enough to make the female brain look like a male’s brain, and that’s something that endures throughout its entire life.”
Sexual development occurs on a spectrum, and these shifts in sexual behavior after allergy exposure are not particularly troubling, according to Lenz. They do, however, help researchers understand the interplay between allergens and brain development and highlight that early life immune activation could be a source of normal variations in female behavior.
“It’s possible these changes could also contribute to things like impaired decision-making, attention, and hyperactivity,” Lenz says.
Lenz was especially interested in the profound changes seen in female brain development, because that’s an area that hasn’t been as well-studied in neuroscience.
“Oftentimes, we are focused on male animals because they appear to be more sensitive to environment changes and also have a higher incidence of conditions such as ADHD and autism. We often frame what we understand about the female brain and female behavior in relation to males. We need to move past that,” Lenz says. “Study of female sexual development has just really been neglected. Even though we know there’s wide variety in girls’ and women’s behavior, we don’t really understand what contributes to those variations.”
Image: Researchers at The Ohio State University found that rats born to moms who had an allergic reaction during pregnancy exhibited unexpected sexual behaviors and experienced brain changes that made them look more like animals of the other gender. Image courtesy of Ohio State University.