Background: Clinical remission of atopic dermatitis (AD) after intake of a low-salt water has recently been reported. Methods: We here investigated the effects of a low-salt water in AD patients with increased intestinal permeability to lactulose. From an initial group of 75 atopic patients, who undertook a treatment in a medical spa center, 12 were included because of abnormal urinary excretion of lactulose (>0.6%), which is absorbed in the enterocytic interspaces, at baseline. The excretion of mannitol with an extraenterocytic absorption was also studied as control. During 18 days, the patients followed a medical spa treatment course, including topical application and oral ingestion of a low-mineral water. Patients were asked not to modify their usual food regimen during the cure. At the end of treatment (day 18), the determination of the excretion of both sugars in urine was repeated. Results: At baseline, the mean urine excretion of lactulose in the study population was 1.21 ± 0.08 SEM. At the end of treatment (day 18), the lactulose concentration in urine diminished dramatically by 55% (mean 0.55 ± 0.09 SEM, p = 0.0005). Urine mannitol was also found to be reduced over the cure period, although to a lesser extent (30%, p = 0.04). Conclusion: This study indicates that low-mineral water normalizes the intestinal permeability of patients with AD.