Katharina Dorothea Kuipers was born in London, England, to Dutch parents. She wanted to become a doctor, and began her career as a chiropodist after winning a scholarship to study at the London Foot Hospital. In 1942, after the death in World War II of her first husband, she enrolled at the Royal Free Hospital. In 1944, she married Tom Dalton, later a Unitarian minister. As a pregnant medical student, she discovered that her usual premenstrual headlines had disappeared, and concluded that high levels of progesterone might have made the difference. After conducting some research, she published her work and coined the term "premenstrual syndrome (PMS)."
Dr. Dalton spent many years working to convince her colleagues in the medical profession that PMS was a real disorder, and helping women get proper treatment. She wrote a book, Once a Month (1978), which became a bestseller. From 1957, she ran her own PMS clinic at University College Hospital, among the first of its kind in the world, and built a large private medical practice.