A new study contradicts the common wisdom of washing a wound with soap and water to prevent infection. According to research published in the New England Journal of Medicine, a low-pressure solution of salt water is a better idea.

The study looked at more than 2400 patients who underwent an operation to fix an open fracture at 41 hospitals around the world during a four-year period. Some of them had their wounds washed out with castile soap and water, while others received a saline solution, both at various pressures.

Patients who received soap and water were more likely to need surgery again in the following year to treat an operation-related infection, or some other kind of problem with the healing process. Almost 15 percent of the soap group needed surgery again, compared to less than 12 percent of the saline group. The researchers didn’t find any differences between patients who received high-pressure cleaning solutions or low-pressure ones.

These results contradict previously accepted guidelines that recommend high-pressure irrigation to remove contaminants from open wounds, and previous studies that found soap to be better at removing bacteria than saline. The majority of the study sample was made up of men, and most had injuries to their extremities, like their hands or feet. The most common cause was a car accident. So it’s possible that the saline solution method might not be as effective for other wounds, but with 2400 patients treated randomly around the world, the low-pressure saline option would appear to be a safe enough method of cleaning—and a much cheaper one, especially for hospitals in developing countries.