Cold sores usually start the same way - first a little painful spot under the skin like a blind pimple.
Sometimes there's a painful tingling a couple of days before, which is called the prodrome.
This usually explodes into a puss-filled blister (or group of blisters) that lasts for a lovely seven to ten days.
Since cold sores are caused by the herpes simplex virus, they're always going to come back.
They're also highly contagious, mostly during outbreaks.
Sharing towels, utensils or shaving razors with someone who has an active fever blister is a great way to contract the herpes simplex virus forever.
Cold sores are at their most contagious from the time they first appear until they have crusted over completely and are no longer seeping.
Most of the time, an outbreak will just clear up on their own.
That doesn't mean you can speed up the process with a dose of a soothing topical cream, but it does mean that there's probably not any reason to go to a doctor for them unless symptoms are incredibly severe, last more than two weeks, or are incredibly frequent.
Occasionally, you may also feel irritation in your eyes - seek medical treatment immediately if this happens as herpes simplex can cause scaring in the cornea that results in blindness.
If you have a outbreak, you should be sure to avoid contact with people who have compromised immune systems, like those with cancer or AIDS.
You should also avoid contact with babies, as they may contract a more serious infection if they are exposed to the virus.
Antiviral treatments are available, but are typically most effective if used very early.
They can shorten the duration a little.
Most cold sore creams are simply soothing and make waiting out the blisters a little more pleasant.