The goal of this clinical trial is to evaluate the feasibility of low-sodium diet to improve eczema severity. The main questions it aims to answer are:

• Does a low-sodium diet improve eczema severity?
• How does a low-sodium diet impact skin sodium concentration?
• Is skin sodium concentration associated with eczema severity?

Researchers will ask all participant to follow a low-sodium diet, then compare sodium tablets to a placebo (a look-alike substance that contains no drug) to specifically examine the impact of altering sodium intake.

Participants will:

• Follow a low-salt diet for the duration of the 24-week study
• Take sodium chloride tablets every day for 5 weeks followed by a placebo every day for 5 weeks after a 2-week washout period, or vice versa
• Complete up to 4 virtual check-in visits
• Visit the clinic 4 times to answer questionnaires, provide bio samples, complete dietary recalls, and undergo non-contrast sodium MRI

The central hypothesis of this proposal is that excess dietary sodium (consumed primarily as salt) is concentrated in the skin as a physiologic response to poor barrier function, and that a low-sodium diet can improve eczema severity.

The study will recruit 40 individuals (10 healthy participants, 30 with moderate-severe atopic dermatitis) and follow them to identify factors associated with skin sodium storage.

All participants will be counseled on how to follow a low-sodium diet for 24 weeks. After 12 weeks on the diet alone, they will be asked to add daily tablets in a self-controlled cross-over design. Participants will be randomized in equal groups to either start with sodium tables or placebo tablets. One group will receive sodium tablets for weeks 13-17, no tablets for a washout period during weeks 18-19, then placebo tablets for weeks 20-24. The other group will receive placebo tablets for weeks 13-17, no tablets for a washout period during weeks 18-19, then sodium tablets for weeks 20-24. Sodium consumption will be evaluated using dietary recall questionnaires and urine biomarkers, skin sodium concentration will be measured using a non-invasive sodium MRI technique, and eczema activity and severity will be measured using multiple patient-reported outcomes and clinician scores.

To test the hypothesis that the low-sodium DASH diet improves eczema severity, we will compare eczema severity before and after the 12-week low-sodium dietary intervention. As secondary objectives, we will also test whether increases in dietary sodium administered as sodium chloride tablets during the second 12-week study period are associated with increases in skin sodium concentration corresponding to eczema severity, and whether there are protein biomarkers in the skin or blood that are associated with changes in dietary sodium, skin sodium concentration, and/or eczema severity.

Inclusion Criteria:

• Participants ages 18 years
• Willing and able to undergo non-contrast MRI.

Exclusion Criteria:

• Contraindications to MRI (such as cardiac pacemakers, claustrophobia, non-compatible intracranial vascular clips, IUDs, or other implants)
• A cardiac event in the past 6 months
• Impaired function of the liver or kidney (glomerular filtration rate <60 mL/min)
• Medications that influence sodium excretion (e.g., diuretics or SGLT2 inhibitors)
• Antibiotic or immunomodulatory medications within the last month
• Contraindications to sodium tablets

(Topical medications used exclusively on the head/neck or hands/feet (e.g., antifungal nail treatment, antidandruff shampoo, acne cleansers) are acceptable. Topical and systemic eczema treatments are acceptable if the participant has been on a stable dose for at least 2 months and still meets the severity entry criteria. Patients on dupilumab will not be excluded if they have been on dupilumab for at least two months and still meet the disease severity inclusion criteria.)

All IPD that underlie the results in a publication

Beginning 1 year and ending 5 years after publication of the results

Researchers interested in accessing data from the project must submit a written resource request via email to the Principal Investigator and sign a Data Use Agreement. De-identified data will be shared through a secure server.

Clinical research coordinators will be masked.