Researchers have studied the phenomenon of ferning in cervical fluid since 1945, when Greek physician Georgios Papanikolaou observed microscopic crystal formations in cervical fluid (mucus). As a result of his work, Papanikolaou was twice nominated for the Nobel Prize and received the Albert Lasker Award for Clinical Medical Research in 1950.
In 1969, Dr. Biel Cassals, a Spanish gynecologist, studied the crystallization of saliva. His presentation to the Barcelona Medical Board proved a relationship between hormonal changes during the female menstrual cycle and the crystallization of saliva, indicating ferning saliva is virtually identical in appearance to the arborization effect of cervical fluid.
The hormone estrogen links saliva patterns to a woman’s fertility. As ovulation nears, estrogen increases and causes the body's sodium levels to rise increasing the salinity of a woman’s saliva. Near ovulation the higher salt content causes the dried saliva to form crystallization patterns as seen under microscope. Both saliva and cervical mucus have shown these patterns.