The Impact of Salt Intake on Sodium in the Skin and Inflammatory Skin Disease

The goal of this clinical trial is to demonstrate the feasibility of a trial that examines the impact of changes in dietary sodium intake on skin sodium levels, atopic dermatitis, and psoriasis. In addition, it aims to generate preliminary data to begin to answer the following questions: 1. Is there an association between skin sodium concentration and atopic dermatitis and psoriasis severity? 2. Are changes in dietary sodium are associated with changes in skin sodium concentration and atopic dermatitis and psoriasis severity? Researchers will 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 13-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 * Visit the clinic up to 4 times to answer questionnaires, provide bio samples, complete dietary recalls, and undergo non-contrast sodium MRI

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 \