Lavender oil works wonders on cold sores. It stops them turning to a blister, if caught early enough and treated enough with the oil.
I control hsv2 outbreaks with healthy diet and exercise. Exercise helps me to relieve stress, thus keeping outbreaks at bay since stress is a major factor in having outbreaks (for me). When I feel an outbreak coming on I apply lavender oil to the area that tingles and within hours the feeling is gone and no outbreak occurs. I've had the same success using tea tree oil. Believe it or not, on an established sore, neither oil hurts, but rather relieves the itch and pain and speeds up the healing process. I've also used lysine supplements as well as an echinacea and goldenseal combo while pregnant.