Factors during sex

    Some people find that the friction of sexual intercourse irritates the skin and brings on symptoms. Using a water-based lubricant can help reduce irritation. Don't use one that contains the spermicide nonoxynol-9, however. Nonoxynol-9 can irritate mucous membranes, such as the lining of the vagina. Oil-based lubricants are a no-no, too. They weaken latex, making condoms more likely to break. Even if the friction of intercourse seems to be a trigger for symptoms, it probably won't cause a flare-up every time you have sex.
    Colds and sunlight. The common cold and sunlight seem to trigger outbreaks of oral herpes (cold sores), but no proof exists that they trigger genital herpes outbreaks.
    Hormones. Hormonal changes, like those that occur in the menstrual cycle, can affect genital herpes outbreaks. No one knows why yet.
    Surgery, weak immune system. Trauma to the body, such as having surgery, may make herpes symptoms appear. It's possible that having a weakened immune system does, too. People whose immune systems are weakened by HIV, for example, tend to have outbreaks more often than people with normal immune functioning do.