Researchers in Sweden are challenging the popular theory, which suggests that greater exposure to bacteria at a young age means less chance of developing allergies.

The study, from the Karolinska Institute, compared allergic responses between ‘dirty’ wild mice, which have been exposed to more bacteria from birth, and ‘clean’, genetically identical, laboratory mice.

The researchers found little variance in the allergic immune response between the two types of mice. In fact, the wild mice exhibited robust allergic reactions when exposed to allergens.

Jonathan Coquet, a main co-author of the study in Science Immunology, said: “This was a little unexpected, but suggests that it’s not as simple as saying, ‘dirty lifestyles will stop allergies while clean lifestyles may set them off.”

Given the immune system similarities between humans and wild mice, these findings could change current medical approaches, such as previous studies directed towards Caesarean-section delivered babies, where supplements with beneficial bacteria have been suggested as good for the newborn’s gut.

Meanwhile, the Karolinska Institute was recently the host of an EARA event to foster greater openness and dialogue about the use of animals in research in Sweden. Find out more about that event here.