The pain from the condition vulvodynia can be so severe that a woman can't sit, ride a bike, wear jeans or have sex. But new research on chronic vulva pain suggests that it can be brought on by repeated vaginal yeast infections, and could eventually help doctors prevent and treat the disorder. Forty percent of mice that experienced three yeast infections in a row developed vulvodynia, the study showed.
"This is the first animal model showing that recurrent infections can cause chronic pain," said study researcher Melissa Farmer, of McGill University in Montreal.
The study, which is published today (Sept. 21) in the journal Science Translational Medicine, suggested that some women develop vulvodynia when yeast infections trigger an overgrowth of nerve fibers in the region.
Around six million U.S. women currently suffer from some form of vulvodynia .
Learning from mice
For decades, doctors have noticed that some women with vulvodynia also experience frequent yeast infections more than three a year. But the link between yeast infections and the chronic pain disorder had not been well-understood.
Farmer and her colleagues turned to healthy female mice to study what happens to the vulva the external female genitalia when multiple yeast infections occur. They gave mice vaginal infections using Candida albicans, the strain of yeast that causes most yeast infections in humans.
Because most women begin treating a yeast infection shortly after symptoms appear, Farmer did the same for the mice, beginning a course of oral medicine after the infection began.
Over the course of the yeast infections, Farmer tested the pain thresholds of the mice by brushing a light hair across their vulvas. Mice in pain jumped at even the lightest touch of the hair.
"During each infection, I saw some sensitivity," said Farmer. "But after the first two infections, the sensitivity levels returned to normal." After the third yeast infection, however, the vulva sensitivity remained.
Seven weeks after the third infection had resolved, some mice still recoiled at the touch of the hair. In mice, pain lasting seven weeks is considered chronic.
While the mice appeared normal, with no outward signs of inflammation, Farmer observed an increase in nerve fibers in the vulva and said that changes within the cells must have resulted from the infections.
Changing women's lives
The study in mice marks a turning point in vulvodynia research with a mouse model and a known cause, scientists can now work toward uncovering the molecular basis of the disorder, and testing treatments.
"The next step is to use the animal model to look at mechanisms," said Chris Veasley, executive director of the National Vulvodynia Association in Silver Spring, Md. "You can begin to study what underlying cellular changes are happening when the mice develop chronic pain."
Veasley hopes that research on vulvodynia's causes and potential treatments will also help raise awareness of the disorder among women.
"This condition is still very stigmatized," Veasley said. "Forty percent of women with symptoms don't seek medical care, and a large majority of health care providers don't know enough about vulvodynia. That needs to change."
She emphasized that vulva pain or pain during intercourse is not normal it should always be checked out by a doctor.
Pass it on: Women with recurrent yeast infections are at risk of developing chronic pain of the vulva and should be aware of the symptoms.
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