Herpes simplex virus (HSV) is the cause of cold sores and genital herpes.HSV-1 most commonly causes cold sores, while HSV-2 typically is the causative strain for genital herpes. Herpes is a DNA virus. Once an initial infection occurs, HSV is with that individual for life - the immune system is unable to clear the virus and it lies dormant in nerves and immune cells. Cold sores near or on the mouth are usually preceded by burning or tingling pain. Skin lesions appear as blisters or open sores on a red base. The lesions take usually 7-14 days to resolve and are painful. Occasionally a flu-like illness accompanies the outbreak. Genital lesions follow a similar pattern of initial outbreak with pain, burning and blistering, followed by slow resolution. The diagnosis of HSV is usually straight-forward. Viral culture of the skin lesion and blood tests may be completed to prove infectivity. Stress, sun exposure, and trauma can all cause recurrences. Many cases of viral reactivation can occur without symptoms. There is no cure for HSV. Symptoms can be controlled and skin lesions treated toward quicker resolution using oral antiviral therapy such as valacyclovir (Valtrex) or famciclovir (Famvir).