With the advent of the Industrial Revolution, and the growth of cities in Victorian England, urban dairies could not keep up with the demand for milk. Unfortunately, transportation from farms in those pre-refrigeration, pre-pasteurization days allowed time for various microbes in the milk to multiply. Some of these microbes produce enzymes that convert the lactose and proteins in milk into smelly, foul-tasting compounds, and farmers had somehow discovered a work-around. Adding “boracic acid,” a mixture of sodium borate (borax) and its acidified derivative, boric acid, countered the milk’s unpleasant smell and off-taste. Mrs. Beeton was aware of this, and assured her readers that boracic acid was harmless, and recommended that they could even preserve their milk longer by adding some themselves. Bad idea!

Boron compounds are not harmless. Indeed, an article in 1887 in The Lancet, the prime medical journal at the time, claimed that “even small quantities of boracic acid are capable of exerting a distinctly injurious action on the human organism.” This, however, was not the major problem. While boracic acid retarded the growth of microbes that caused the unpleasant sensory properties, it did not prevent the growth of disease-causing organisms. The longer the milk was kept, and boracic acid allowed for that, the more time the tuberculosis bacteria had to multiply. Infection of Victorian children with bovine tuberculosis was common, and many deaths could have been spared had boracic acid not contributed to the illusion of safety.

Milk was killing children on this side of the pond as well. Here, the problem wasn’t the masking of spoiled milk with boracic acid, it was contaminated milk from cows kept in filthy conditions and fed brewery waste “swill.” New York, like London, had become a huge, bustling city with an ever-increasing demand for milk to feed infants. Distilleries in the city produced large amounts of alcoholic mash left over from making whiskey, something that did not go unnoticed by milk producers. Dairies sprang up around distilleries where cows were fed the “swill.” To maximize profits, the animals were squeezed into narrow stalls where they were covered with flies and wallowed in their own excrement. No wonder they became so sick they could hardly stand. Even the milk they produced looked sickly. To alter its bluish colour, plaster of Paris and molasses were added and flour was used as a thickener. A New York Times editorial in 1858 described “swill milk” as “bluish-white compound of true milk, pus and dirty water,” produced by “running distillery slops through the udders of dying cows and over the unwashed hands of milkers.” The Times estimated that every year some 8,000 infants died from drinking swill milk.