The purpose of this study is see if Transcutaneous Electrical Nerve Stimulator (TENS) units help decrease endometriosis flare pain. TENS units have a 510K and are intended for relief of pain associated with sore or aching muscles of the lower back, arms, or legs due to strain from exercise or normal household and work activities.

Participants will complete surveys, record pain, medication use and bleeding in an online diary during endometriosis flare ups for 3 months without using the TENS unit. After the first 3 month period of time, a TENS unit will be given to participants to wear and again, record pain, medication use and bleeding in the online diary during endometriosis flare ups for and additional 3 months while using the TENS unit.

The investigators propose to conduct a cross-over clinical study to evaluate the effectiveness of TENS units on the management of endometriosis flare-related pain. Subjects will participate in a 3-month "baseline" period (no TENS unit use for endometriosis flares) and then cross-over to a 3-month "treatment" period (TENS unit use for endometriosis flares).

Potential subjects will be pre-screened in the Penn State Minimally Invasive GYN (MIGS) Surgery Clinic for pathologically diagnosed endometriosis and from the Penn State MIGS endometriosis database. Potential subjects will then be called to evaluate the remainder of the inclusion and exclusion criteria. If fulfilled, potential subjects will follow up at the enrollment visit (Visit 1) where consent is reviewed and signed. The baseline QOL and FSFI REDCap surveys will be completed at this visit. Subjects will be set up to receive automated links to complete diary entries and surveys directly in REDCap.

Prior to initiating TENS unit use for endometriosis flare-related pain, subjects will record daily entries into RedCap during episodes of endometriosis flares for 3 months. Each entry will record their VAS pain score as well as medication intake and bleeding profile.

Subjects will then be mailed the TENS unit at the 3 months mark into the study. Subjects will then complete entries with TENS use at their discretion for the following 3 months and record TENS unit use duration, frequency, and side effects in addition to the documentation of pain, medication and bleeding. At the end of the study, subjects will complete a QOL and FSFI survey.

Inclusion Criteria:

1. Females ages 18-45 years at time of enrollment
2. A surgical diagnosis with direct visualization and/or histopathologic confirmation of endometriosis
3. Average monthly endometriosis pain flare
4. Naïve TENS user

Exclusion Criteria:

1. TENS device exclusion:

   1. Implantable devices (pacemaker, Interstim, etc.)
   2. Cardiac arrhythmia
   3. Open skin sores over areas of placement

2. Pregnancy

3. Nursing or trying to conceive at this time

4. Post-operative <12 weeks from abdominal or pelvic surgery

5. Planned surgery or hormonal medication changes for duration of study if applicable

6. Non-English speaking or inability to read and understand English

7. Prisoners