Eczema: Too much sodium may increase atopic dermatitis risk

By Staff 8 Min Read

  • Nearly 32 million people in the U.S. have some form of dermatitis, most of whom are children.
  • A new study links excess sodium intake with the development, activation, and intensifying of atopic dermatitis, or eczema.
  • When sodium is stored in the skin it can trigger inflammatory pathways that result in atopic dermatitis.
  • The study demonstrates a link between high salt intake and atopic dermatitis, but environmental factors and other causes also play a role.

Atopic dermatitis (AD), commonly known as eczema, is a collection of inflammatory skin conditions.

Symptoms of AD may include rashes, dry and scaly or cracked skin, itching, skin infections with open, weeping sores, as well as discolored skin and blisters. The condition is caused by certain triggers that vary from person to person.

Now, a new study from researchers at the University of California, San Francisco (UCSF), suggests that high levels of dietary sodium may raise the risk of developing atopic dermatitis.

The study found that people with a 1-gram increase in estimated 24-hour urine sodium excretion were 11% more likely to develop atopic dermatitis, 16% more likely to have active symptoms of existing AD, and have an 11% higher chance of increasing AD severity.

The study is published in JAMA Dermatology.

“[Atopic dermatitis] encompasses a spectrum of inflammatory processes and is triggered by various environmental factors,” Katrina Abuabara, MD, associate professor of dermatology at UCSF and senior study author, told Medical News Today. “This study was the first step in that we were able to show an association between dietary salt and AD in a large population.”

The study was a cross-sectional investigation of data for 215,832 participants in the UK BioBank aged 37 to 73, with a mean age of 56.52 years. Of this group, 54.3% were female. The cohort included 10,839 people who had AD, while the remainder did not.

Urinalysis of participants established that the mean estimated 24-hour urine sodium secretion was 3.01 grams, which represented about 90% of the previous day’s dietary sodium intake. The researchers observed that for every 1 gram of sodium above that mean, atopic dermatitis risk increased.

“It is hypothesized that sodium is stored in the skin to prevent water loss, and may help prevent infection. However, it can also activate cells in the immune system, triggering some inflammatory pathways and removing the ‘brakes’ from others,” Abuabara explained.

“For reasons we don’t yet understand, some people may be more susceptible to the effects of sodium, just as people differ with respect to their susceptibility to the effects of sodium on blood pressure. I think it is important to have experimental evidence that reducing dietary salt can actually improve eczema symptoms before we recommend dietary changes specifically for eczema.”

— Katrina Abuabara, MD, senior study author

Michelle Routhenstein, RDN, a preventive cardiology dietitian at, not involved in the study, noted a limitation of these findings.

She said the study involved only one urinary sample per participant, which was used to estimate urine sodium excretion for a single 24-hour time period. This estimated 24-hour sodium excretion was then used to gauge participants’ typical dietary sodium intake.

Without more samples collected over a longer term, the study’s ability to assess long-term sodium intake accurately was limited, Routhenstein said.

The National Eczema Foundation reports that 31.6 million people in the U.S. have some form of eczema. About 1 in 10 people experience eczema during their lifetime.

Atopic dermatitis is most common in children, affecting roughly 1 in 5. About 9.6 million children under the age of 18 in the U.S. have AD, with a third of them experiencing moderate-to severe symptoms. Roughly 7.5% of American adults, or 16.5 million people have AD, about 40% of whom have a moderate or severe form.

Because the causes of AD are multifactorial and vary based on the individual, it is unlikely that sodium is the only culprit.

Abuabara cited a recent study that identified a range of environmental factors — collectively called the “exposome” — that may trigger the condition.

Other foods have also been associated with developing AD, Routhenstein noted.

“Atopic dermatitis may be triggered by different foods, depending on the person, and a food elimination trial can help determine the potential trigger. Trigger foods can include food additives, preservatives, dairy, wheat, eggs, fish, or shellfish,” she said.

Routhenstein cautioned that anyone attempting a food elimination diet to search for their AD trigger do so under the guidance of a registered dietitian to avoid nutrient deficiencies.

The findings of this new research suggest that reducing salt intake could be a simple way to prevent or alleviate atopic dermatitis.

Eliminating dietary sodium altogether is not feasible. Sodium naturally occurs in many foods, and salt, the biggest source of dietary sodium, is often added to food processing for preservation and flavor. However, Routhenstein explained that not getting enough sodium could be harmful to health.

“If you are excessively sweating or having chronic diarrhea where the loss is more than intake, it may be a concern. This can lead to fatigue, muscle weakness, nausea, vomiting, headache, confusion, and seizures,” she said.

“The other issue that may arise with a potentially no-salt diet is an iodine deficiency if you are not consuming other sources of iodine like dairy, seaweed, or fish. More concentration should be placed on what you are adding to the diet to help address inflammation and ensure nutrient adequacy,” Routhenstein noted.

Many table salts are iodized, meaning they contain small amounts of added iodine to help prevent iodine deficiency in the general population.

Routhenstein recommended that a person adjust to consuming less sodium by replacing it with other pleasing flavors.

“Adding flavor such as favorite herbs, spices, citrus juices like lemon or lime, vinegar such as balsamic or apple cider, and garlic and onions is important when reducing salt intake, ensuring dishes maintain depth and tanginess without relying solely on salt.”

— Michelle Routhenstein, RDN, preventive cardiology dietitian

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