How long does it take to develop lesions after exposure to cold sores? my boyfriend has developed cold sore blisters and i think i have been exposed. how long before i can expect to see blisters forming if i do have the virus?

Cold : Cold sores or fever blisters are caused by herpes simplex virus type 1 (hsv-1) and are extremely common. Most people become infected as an infant or small child when kissed or by sharing eating utensils with an adult who has the virus. The virus is most contagious when someone has a cold sore, but can still be passed along by someone who does not. Many people do not even know that they are infected because the virus can "hide out" in the nerve cells for very long periods of time - for some people it hides out forever and they never get a cold sore. For others, the virus can "wake up" at any time and that's when a cold sore happens. No one knows exactly what causes a cold sore to appear - sometimes stress, illness, fevers, colds, sunlight, cold weather, menstruation, certain foods, allergies, you name it! they usually last 7-10 days and are more of an annoyance than a danger unless you have a weakened immune system or contract a bacterial infection on top of the cold sore. Legal disclaimer: I am providing this general and basic information as a public service and my response to this question does not constitute a doctor-patient relationship. For any additional information, advice, or specific concerns, please speak with your own physician. The information provided is current as of the date of the answer entry.

Week to 10 days: In addition the best time to treat a cold sore is before you see it. A tingle or itch will usually start first in the lip area and that is the time to start whichever medication your doctor recommends.