They found that a large number of cases where patients swallowed high-concentration peroxide resulted in critical illness, some with continued disability or death.
Hydrogen peroxide is a mild antiseptic, commonly found in household concentrations of 3% to 5% to disinfect minor cuts, scrapes and burns.
As a mouth rinse, it helps remove mucus or relieves minor mouth irritation. When applied to an affected area, it releases oxygen-causing foam, which helps remove dead skin and disinfect the area.
High-concentration peroxide -- greater than 10% -- is most often seen in commercial settings, for example to store or prepare food, and is often labeled "food-grade hydrogen peroxide." It is also used as part of complementary or alternative medicine therapies, which use non-traditional medical treatments with or instead of standard medical care.
"Peroxide ingestion cases are difficult to manage, because not a lot of research has been done on these types of cases," said the study's lead author, Dr. Benjamin Hatten of the University of Colorado School of Medicine. After encountering numerous ingestion cases over the course of his career, he set out to increase knowledge about peroxide and provide the medical community with answers regarding care for ingestion patients.
In the alternative and complementary medicine communities, the ingestion of small amounts of diluted, high-concentration hydrogen peroxide, a form of "hydrogenoxygenation" therapy, has been promoted for a range of uses from cleansing the digestive tract and detoxifying to curing cancer.
However, the effects of the claims have yet to be scientifically proven.
"This is not a safe substance," Hatten warned about high-concentration peroxide. "What I hope this study shows is that there are no scientific benefits to ingesting it, and there are very bad outcomes associated with it."
In most cases of exposure in the study, patients swallowed the liquid unknowingly, mistaking it for water. Although high-concentration peroxide is meant to be used by the dropperful, researchers found many instances in which it was stored in a clear vessel in a refrigerator and looked like water.
Unintentional hydrogen peroxide exposure is common. In 2015, the American Association of Poison Control Centers said in its annual report that there were 7,257 cases of peroxide exposure reported in that year, and of those 92% of them unintentional.
Hatten's study recommends storing high-concentration peroxide in its original container and adding both child-resistant capping and a colorizing agent to head off accidental ingestion.
The risks of ingesting high-concentration hydrogen peroxide should not be taken lightly, Hatten said.
"Although these types of cases are rare, people are not aware that this happens, because the research has been limited," he said.
After consuming high-concentration peroxide, patients in the study experienced conditions including seizures, altered mental status, respiratory distress, stroke and pulmonary embolism and heart attacks.
Even a mouthful or two of concentrated hydrogen peroxide led to critical illness caused by a suspected embolism, a vessel blockage, in 13.9% of cases studied, the study said.
Severe long-term outcomes, including continued disability or death, were found in 20 (6.8%) of the 294 cases reported to US poison centers.
"It is not an edible substance. It is very dangerous when you take a high concentration of hydrogen peroxide," said Dr. Cathleen Clancy, associate medical director at the National Capital Poison Center, who was not involved in the new study.
"To put it in perspective, when you consume 1 milliliter of 3% hydrogen peroxide, it can release 10 milliliters of oxygen," she said. "When you put a high concentration of hydrogen peroxide into the blood vessels, it can cause an embolism, which is a collection of air in the blood vessels that can cause a stroke."
Most poison centers recommend hyperbaric oxygen therapy for gas embolism from high-concentration peroxide ingestion, but patients may have difficulties getting to one as soon as possible.
"One of the biggest issues in treatment can be getting patients into a hyperbaric chamber," Hatten said. "Most cities don't have hyperbaric chambers, and the ones that do only use them for wounded care and not for emergencies."
Although the research is limited, the study concludes that it is likely that hyperbaric oxygen therapy is most effective when performed early in treatment. Hatten says future studies should focus on hyperbaric oxygen as an effective form of treatment.