Herpes flare-ups can be caused by a variety of factors, including illness, stress, hormonal changes, and exposure to sunlight. Other triggers may include fatigue, physical exertion, injury, exposure to cold, surgery, and low immunity. Menstrual periods can also trigger genital herpes outbreaks in women. Its important to note that triggers may vary from person to person, and doctors are not certain how much lifestyle affects herpes symptoms. If you think certain factors trigger your disease, its best to discuss with your doctor what you should do about it.