Poison for Penitence: A Hydrogen Peroxide Experiment on Infants in Dublin’s Regina Coeli Hostel

Maya Conners

On October 18, 1947, the medical officer of Regina Coeli Hostel wrote: “Of 14 infants to whose feeds Hydrogen Peroxide was added, 5 were admitted to St. Clare’s, while of 15 infants to whose feeds was added sterile water, and therefore taken as controls, 9 were removed to St. Clare’s Hospital. There was one death in each group.”^[1] This horrifying narration of the administration of hydrogen peroxide to newborn infants describes the results of a covert medical experiment inside the Regina Coeli Hostel, a mother and baby institution near Dublin’s city center. Using clinical, emotionless language, the medical officer Dr. O’Dea reported the experiment’s deadly results. Though aimed at curing gastroenteritis in the Hostel’s infants, who were particularly susceptible to the disease, the trial was a flagrant case of unscrupulous treatment of a vulnerable group. The use of the Regina Coeli infants as test subjects in a dangerous experiment indicates they were disposable to the city, an attitude that mirrored the social marginalization of their mothers.

Philanthropist Frank Duff and the Legion of Mary Charity founded Regina Coeli in 1922 to house unmarried mothers.^[2] Like many similar institutions, the Hostel was a workhouse designed to reform women deemed undesirable by society.^[3] In the 1990s and early 2000s, survivors and activists exposed countless cases of abuse and mistreatment within Ireland’s maternity institutions. Regina Coeli Hostel, however, was acclaimed for its unique custom of encouraging pregnant residents to keep their babies, even allowing women to return with infants after birth or bring children with them.^[4] But the Hostel was not the haven it appeared. The hydrogen peroxide experiment illustrates how mother and baby homes like Regina Coeli exploited not only the women deemed “first offenders” by Irish society but also their children, as an extension of that stigma.^[5] When Dublin experienced widespread illness, the children in Regina Coeli suffered – and not just because of disease.

In the wake of a city-wide outbreak of gastroenteritis in 1946, Dublin’s infant mortality rate was exceedingly high, especially in mother and baby institutions.^[6] The following year, the Gastroenteritis Control Section, desperate to find a solution, began their medical experiment in the Hostel. Originally described as the “hydrogen peroxide treatment of milk,” the trial used the toxic chemical hydrogen peroxide as a bactericidal treatment in the stomachs of infants with gastroenteritis.^[7] It was intended for eventual use on children in the South Crumlin area. Unsure of the ramifications of using the treatment on the public, however, the medical officer suggested conducting a trial first. An institution like Regina Coeli Hostel was an ideal location – central to Dublin, and able to offer experimental control.^[8] The Hostel itself suffered various bouts of disease, with one inspector stating that Regina Coeli had at least one outbreak of typhoid or gastroenteritis per year.^[9] Various remarks by O’Dea in 1947 suggest that he knew hydrogen peroxide could be dangerous. In a letter of correspondence with the city clerk, he alluded to the ‘destructive’ chemical qualities of hydrogen peroxide, stating that even though he doubted the treatment would cause harm, it was first going to be tested in Regina Coeli regardless.^[10] The word ‘destructive’ in this letter was legible but crossed out in the original handwritten note in blue pen. This suggests that the medical officer may have intended a more neutral phrasing when reporting on the experiment and felt that ‘destructive’ was too bold a word. However, the word’s presence reveals his knowledge on the corrosive properties of hydrogen peroxide. This statement demonstrates that, while the medical officer was relatively assured that the hydrogen peroxide treatment was safe, he promoted experimentation on the hostel’s babies, substantially endangering their health.

In the summer of 1947, the Hostel began to feed infants milk mixed with hydrogen peroxide, recording results through hospitalizations and deaths. In O’Dea’s report, he summarized the experiment’s progress to the Minister for Health, revealing the fourteen hospitalizations and two deaths of the Regina Coeli infants.^[11] Files on the experiment did not indicate each infant’s reason for hospitalization, making it unclear whether their health declines were due to gastroenteritis or a toxicity response to hydrogen peroxide. It was not noted whether each baby had gastroenteritis at the time of ingestion either. Altogether, the undetailed documentation of the babies’ individual conditions and reactions denote how haphazardly the Gastroenteritis Control Section conducted the experiment. Despite the large number of infants hospitalized following the trial, O’Dea quickly described its results as “not, on the face of it, impressive,” reflecting the unconcerned and rather distanced nature of the study.^[12] While the Gastroenteritis Control Section was aware of possible malignant effects, they were more focused on the possibility of finding a cure than the wellbeing of the involved babies.

As fall of 1947 arrived, the experiment was still running in Regina Coeli Hostel, though there were doubts about the results. The hydrogen peroxide treatment neither cured the infants nor prevented them from getting gastroenteritis. On October 18, 1947, O’Dea speculated on the possible reasons for the ineffectiveness of the milk treatment. He suggested that the hydrogen peroxide had been added to the infants’ feeds too soon before consumption, signifying that the chemical had not had sufficient time to “exercise any bactericidal effect.”^[13] The Hostel carried on the experiment, having adjusted their regimen, and began to consider the application of the hydrogen peroxide treatment to the public. The medical officer cautiously argued that they needed strong evidence of the treatment’s value before publicizing it.^[14]

The experiment went on into the early months of 1948, even in the face of unremarkable results. By the beginning of 1948, the medical officers orchestrating the experiment had not received satisfactory results and hesitated to continue it. On February 18, 1948, O’Dea stated in a letter to the city clerk that they were reconsidering the final goal of applying the milk treatment to South Crumlin due to the unconvincing results yielded in Regina Coeli. The Gastroenteritis Control Section deemed it unwise to publicize the treatment, and by March 1, they decided that the trial “might now be regarded as finished.”^[15] In Regina Coeli, the use of hydrogen peroxide was ineffective as a bactericide for gastroenteritis, but it also interfered with the diets and potentially the health of the treated infants. This calculated use of a vulnerable population for the trial evidences the mistreatment of the infants in the institution and how the combination of biomedicine with the culture of moral regulation in twentieth century Ireland allowed it to happen.

We do not know how the infants were selected for the trial, or whether their mothers had given them up or not. If there were unseparated infants, where were their mothers in these decisions? Considering the social and financial vulnerability of women in Regina Coeli, they were likely under pressure to consent for fear of facing further social discrimination. In mid-twentieth-century Ireland, having a child outside of marriage was a social crime for women, a phenomenon that largely contributed to the founding of mother and baby institutions.^[16] The stigma around being in any institution was, and often remains, a source of shame for women. Coupled with the economic disadvantage of being working class or without a home, these factors further allowed medical officers and the Gastroenteritis Control section to exploit Regina Coeli’s women and infants without questioning.

In some cases, the mothers at Regina Coeli were perhaps unaware of the experiment, as the Hostel’s staff were involved in feeding the babies milk.^[17] Many of these women may have trusted the doctors appointed to the experiment to care for their sick children, without any idea or assumption that it could be harmful. Reports highlighted in Leanne McCormick’s Gender and History article show that several women preferred to stay at Regina Coeli over other institutions due to the small freedoms they were allowed only there, like smoking and brewing their own tea.^[18] A desire to remain in a more comfortable place, even one with “poor living conditions,” as described in an inspection, may have enticed them to stay.

When Irish society’s ostracization of unmarried mothers met the need to implement rapid biomedical solutions to contain the spread of a contagious disease, doctors experimented on Regina Coeli’s infants with a toxic chemical, treating them like lab rats rather than the sick children they were. The months-long span of the trial demonstrates that, to the Gastroenteritis Control Section, the Regina Coeli infants were of less value than children living outside of mother and baby institutions. To some researchers, their high mortality rate itself indicates “a complete lack of concern” for infants born in institutions.^[19] The exploitative use of these infants certainly denotes a systemic disregard for the wellbeing of those in institutions. This experiment not only exposes a trend of medical negligence in Regina Coeli but also showcases the greater cultural phenomenon of stigma against unmarried mothers that made it possible under the approval of the city’s medical officers. The disregard for the Hostel’s infants aligns with a long history of scholarship that has demonstrated the mistreatment of unwed mothers and their children in supposedly benevolent institutions.The existence of this experiment, one so exploitative and irresponsibly conducted, is a stark reminder of the long history of oppression of Irish women and their children who paid the price.

Featured image courtesy Mira Fialkova.

Maya Conners

Maya Conners is an undergraduate student at St. Olaf college in Minnesota. She is pursuing dual majors in psychology and Spanish, and hopes to follow a PhD track in future schooling. She spent January of 2026 participating in a study abroad program called "Love and Sex in Modern Irish History," where she conducted archival research in the National Archives of Ireland.

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