Is it dangerous if a 7 week old baby gets a cold sore?

Could be : If it became disseminated -spread all over.

How do you know? : Please see your pediatrician for a proper diagnosis. It's exceedingly unlikely that your baby has a cold sore, since he needs to get herpes gingivostomatitis first. There is another explanation.

How do you know?: Seven week old babies don't get cold sores. They need to get herpes gingivostomatitis first. This childhood infection usually occurs in the latter half of second year of life onto young adulthood. So what you see is something else. If a baby gets a serious desseminated herpetic infection it is usually already ill with something more serious. See your pediatrician.