Background: Dry and atopic skin requires skin care with lipid-rich emollients and moisturizing bath or shower oils. However, it has been shown recently that some bath oils may even impair the skin barrier. Objective: To investigate the skin-irritating potential of a new bath oil containing a lipophilic St. John’s wort (Hypericum perforatum) extract. Methods: In this single-center, randomized, double-blind, prospective study, 3 bath oils together with positive and negative controls were applied under occlusion on test areas on the volar forearms of 18 volunteers (visit 1). After 24 h, the tapes were removed, and the test areas were evaluated by a visual score and the instrumental measurement of skin erythema and transepidermal water loss (TEWL) using a Mexameter and a Tewameter (visit 2). The test substances were applied a second time, and the measurements were performed after another 24 h (visit 3). Results: The positive control, 1% vol/vol sodium lauryl sulfate (SLS), caused a significant increase in skin erythema and TEWL. In contrast, distilled water as a negative control did not influence these parameters. The new bath oil containing St. John’s wort extract and 1 of the other 2 commercial products were not different from the water control. The third bath oil displayed a skin-irritating effect similar to SLS. Conclusion: The results of this study confirm the different skin-irritating potential of bath oils and demonstrate good skin tolerance of the new bath oil containing St. John‘s wort extract.