In the 1970s, a combination of new synthetic materials and huge market competition led to an arms race among tampon manufacturers. There was a drive to be the most absorbent, the most leak-proof. Rely tampons, manufactured by Procter & Gamble, were highly absorbent, and expanded wide to prevent leaks. They quickly became a market leader owing to the innovative design and super absorbency.

Meanwhile, in the late 1970s, something else happened: a new syndrome was identified and named. Paediatrician James K. Todd reported an illness among childen aged 8-17. The childen had developed a condition after infection with Staphylococcus Aureus. He suspected toxins caused by the bacteria. He called the disease Toxic Shock Syndrome (TSS)

Once TSS was named and described, physicians across the USA began to notice it. And they spotted something unusual: the vast majority of cases were recorded in women, and onset of symptoms tended to take place within a few days of their periods.

An investigation was launched in 1980, and identified that menstruation-related TSS was caused by tampons. And a September 1980 report by the CDC identified that up to 75% of these cases were caused by one specific brand of tampon: Rely.