A salty diet may increase eczema in adults, study finds

Adults who eat a salty diet appear to have a higher risk for eczema, according to a study by researchers at the University of California at San Francisco.

An estimated 1 in 10 Americans will develop eczema, or atopic dermatitis, which causes the skin to become irritated, inflamed and itchy. But according to the National Institutes of Health, the cause of the rash remains unknown. Dermatologists say the study, published on Wednesday in JAMA Dermatology, will lead to further research regarding how salt may play a role in the skin condition.

“We really wanted to understand triggers for atopic dermatitis,” said Katrina Abuabara, the lead author of the study and an associate professor of dermatology in the School of Medicine at the University of California at San Francisco. Some estimates show the prevalence of eczema has increased over the past century in ways “that can’t be explained by genetics alone,” she said.

• Researchers found a one-gram increase in estimated daily salt intake was associated with an 11 percent higher risk of eczema in adults.
• The findings are based on urine samples and medical records from 215,832 adults in the U.K. Biobank. Five percent, or 10,839, of the participants were diagnosed with eczema and prescribed treatment for the rash.
• More sodium detected in the urine samples was associated with a higher likelihood of an increased severity in eczema, as well.

What we know about eczema and salt

The results of the UCSF study amount to a “smallish increase in risk” and more research is needed, Abuabara said. But there are a few reasons salt intake may be associated with eczema, she said. Researchers have found sodium is stored in the skin. Sodium can trigger inflammation in the body, and epidemiological data suggests a person’s diet is associated with eczema.

A study published in 2013 of children around the world found regularly eating fast food — often high in salt — to be associated with higher prevalence of eczema. But fast food is also “full of other things” that could explain that association, Abuabara said.

“I don’t think all eczema is related to salt,” Abuabara said. “I think this is one piece of things that’s probably a trigger for some people.”

Abuabara plans to conduct experiments to see whether a reduction in sodium is associated with a reduction in eczema severity.

“We don’t yet know if reducing sodium intake would reduce eczema severity,” she said. “So we’re doing more work before we can specifically recommend that or recommend a particular diet.”

The limitations

The study’s findings don’t show that salt causes eczema but rather show an association between salt and the condition. Most study participants were White (95 percent), and volunteers in the U.K. Biobank skew older and tend to be healthier than the general population.

The National Eczema Association and the National Institute on Aging contributed funding for the study. Abuabara has also received research funding or consulting fees from Pfizer, La Roche-Posay, Target RWE, Sanofi, Nektar and Amgen.

What the experts say

Saranya Wyles, a dermatologist and the director of the regenerative dermatology and skin longevity lab at Mayo Clinic in Rochester, Minn., said the findings “are a great start for hypothesis generation” but the data is based on a one-time urine sample of the participants and the results are not definitive.

“We can say this is testing a potential hypothesis, but I do not think this is definitive,” Wyles said. “We have to be cautious of how it’s interpreted.”

Bruce Brod, a clinical professor of dermatology at the Perelman School of Medicine at the University of Pennsylvania, said atopic dermatitis is most common in children, but the study’s participants are adults with an average age of 56 years old.

“It’s hard to change treatment paradigms based off this study,” Brod said. “But I think the study represents a nice piece of bio-epidemiologic work that potentially lends itself to further study down the line.”

How to treat eczema

Eczema, or atopic dermatitis, deals with the dysfunction of the skin barrier, said Brod. How often a person bathes, the temperature or humidity where someone lives and what they’re exposed to at home or at work all play a role.

“We love our long, hot showers,” he said. “While it might be a time for relaxation, heat and hot water, and soap, can aggravate atopic dermatitis.”

Tobacco smoke, other air pollutants and certain fragrances in skin products and soaps can also lead to atopic dermatitis, according to NIH.

Eczema tends to develop in the folds of skin, such as on the inside of arms and the backs of knees, said Wyles. And eczema can lead to a “itch-scratch cycle” in which itching the rash leads to more inflammation, which further compromises the skin barrier, Wyles said.

Moisturize your skin regularly to protect the skin’s barrier, Wyles said. If the rash is “actively inflamed,” talk to a dermatologist about getting topical steroids or other treatments. And, in more severe cases, there are oral and injectable medications available.

“The most important thing is barrier protection, giving your skin barrier hydration,” Wyles said. “People can even do over-the-counter moisturizers for eczema.”