Background Some women suffer cyclical recurrences of genital herpes (c-RGH) immediately prior to menstruation, which are effectively prevented using aciclovir in the luteal phase only. This is more likely to occur in perimenopausal women whose immunity is diminished by premenstrual dysphoric disorder (PMDD), which is treatable with transdermal estradiol.

Aim To observe the frequency of herpes recurrences in women commencing estradiol treatment for perimenopausal PMDD.

Methods 12 perimenopausal women median age 41 years (range 36–45) presented between 2006–15, each meeting the criteria for PMDD subsequently defined in DSM-5. Each had at least 4 consecutive monthly episodes of c-RGH (culture-proven HSV2) before some took luteal-phase aciclovir, then all switched to transdermal 17-beta estradiol gel 0.5mg daily for 14 days in the luteal phase or continuously for those using Mirena. Subjects self-reported mood with a modified daily symptom chart and herpetic symptoms over 9 months follow-up during which no aciclovir was taken pre-emptively. Intention-to-treat analysis included 10 cycles where treatment was omitted in error and both conditions recurred.

Results All women experienced substantial or complete relief of PMDD in all but three treated cycles. Only 13 symptomatic c-RGH episodes occurred on treatment in 108 woman-months’ observation.

Conclusion Transdermal estradiol treatment is a novel and biologically plausible method of preventing cyclically-recurrent genital herpes as it stabilises the hormonal milieu and diminishes immune suppression caused by PMDD.