Over the past 50 years, the frequency of allergies and autoimmune diseases has risen rapidly, but it’s not clear why. In a study published today (February 20) in Science Translational Medicine, researchers point to a possible culprit: salt. The authors found in lab experiments that high concentrations of sodium chloride can influence the differentiation of T helper 2 (Th2) cells, the immune cells responsible for allergies, and that high levels of salt are present in the affected skin of people with atopic dermatitis, an allergic skin condition.

“These are the sorts of studies that I love because it’s so completely different, and that’s what we need because really there hasn’t been much progress in understanding this epidemic of allergic disease,” says Charles Mackay, an immunologist at Monash University in Australia who did not participate in the work. In looking “at why we get an allergy or atopic dermatitis, I try to think of the environmental factors,” he adds. This study “is an interesting new angle to Th2 immunity.”

Hay fever and atopic dermatitis have both increased more than two-fold since the 1970s, an upsurge that researchers do not attribute to greater awareness or diagnosis. This recent increase in the incidence of allergic diseases is much too fast to be explained by genetic changes, so it’s more likely to be due to an environmental or behavioral cause, coauthor Christina Zielinski of the Technical University of Munich tells The Scientist. “One thing that also changed within the last fifty [to] sixty years is our diet. We are eating much more fast food, and this also includes much more salt, so that’s how we became interested in the question of whether salt can modulate the immune system,” she says.

The full story appeared in The Scientist: Exploring Life, Inspiring Innovation.  You can read the same by clicking on the link.