What causes cold sores?

Herpes simplex: Real cold sores, which usually occur on the edge of the lips, are caused by herpes simplex virus. This is contagious by touch, and that is touching anywhere. So if you have active cold sores, you need to practice good handwashing anytime you might have touched the sore. Unfortunately, you can also spread them when you don't even have an active sore, in your saliva.

Cold sores: Actually, there are a couple of lesions people call "cold sores". 1) the painful red ulcerations in the mouth that stay around a couple of weeks and the go away - they are actually multifaceted. One possible factor is vit b deficiency. Another is a reaction to sodium lauryl sulfate (in most tooth paste. 2) canker sores on the outside of the mouth caused by a type of herpes virus - which are contag.

Herpes: Human herpes virus type i. This is the classic cold sore or fever blister that pops up under stress of infection or sun light irradiation. It occurs on the junction between mucous membrane and skin as on lip or nasal area. Aphthous ulcers and canker sores occur only on mucous membranes. They're due to other viruses. The only cause for fever blisters is hhv-i.