Pain Relief From Dysmenorrhea Employing taVNS

Inclusion Criteria: * Regular menstrual cycle (28 days ± 7 days); * Average moderate menstrual pain (with 4 - 7 NRS scores); * History of over-the-counter (OTC) analgesic use for the treatment of menstrual pain (at least 1 IBUPROFEN for the first two days); * 4 consecutive monthly menstrual cycles; * Non-pregnant status; * Agrees to use adequate birth control during the trial; * Otherwise, healthy; * Agree not to participate in any other clinical trial while enrolled in this trial ; * No facial or ear pain, no recent ear trauma, no metal implants including pacemakers; * Normal ECG, Heart Rate and Blood Pressure (systolic BP 105-130, diastolic BP 60-90, heart rate per min at rest 60-85); Exclusion Criteria: * Currently under medications (except for analgesic medication for menstrual cycle); * Use of oral contraceptive; * Secondary cause for dysmenorrhea (i.e., endometriosis, adenomyosis, uterine fibroids, or infection); * Unstable or serious illness (e.g., kidney, liver, GIT, heart conditions, diabetes, thyroid gland function, lung conditions, chronic asthma, diagnosed psychological or mood disorder, hypertension, any bleeding disorders, recent surgery, or concurrent blood thinning treatment); * Current malignancy or treatment for malignancy within the previous 2 years; * Pregnant or lactating women; * Active smokers, nicotine use, or drug (prescription or illegal substances) abuse; * Chronic past and/or current alcohol use (\>14 alcoholic drinks per week); * Any condition that in the opinion of the investigator, makes the participant unsuitable for inclusion; * Unwilling or unable to comply with protocol; * Active genitourinary infection in the last four weeks; * Unable to read or comprehend the informed consent; * Unwilling to complete study procedures; * Participated in any other clinical trial during the past 1 month; * Personal or family history of seizure, mood, or cardiovascular disorders; * Allergic reaction to surface electrodes.