Anyone who has ever had a cold sore will undoubtedly agree on one thing: they're the worst.
Not only are they embarrassingly visible, what many cold sore non-sufferers don't realise is they are are bloody painful as well.
But what exactly are cold sores, anyway? And what can you do to prevent them?
Cold sores 101
"Cold sores are caused by a virus called herpes simplex virus and are passed on usually by direct contact from someone who is shedding the virus," Cheryl Jones, Professor of Paediatrics at The University of Sydney and Marie Bashir Institute for Infectious Diseases and Biosecurity, told The Huffington Post Australia.
"For someone to effectively pass on the virus, you have to have breaking in your skin or a break in the lining in the lip or eye or genital area. The cracks can be quite small, and you may not know you have them."
Where you can get them
For those who read the above and thought, 'eyes!? I can get cold sores in my EYES!?' the answer is yep -- you can get them pretty much anywhere.
"Where the virus entered the skin, the very first time the virus enters your body, it travels up to your sensory nerves, where it largely lives forever," Jones said.
"When you get a break out, it may not be at the exact spot where it entered.
"Common sites are around the lips, the eyes, and again, the genitals. You can also get them in your fingers -- something we call herpetic whitlow -- which is basically herpes of the fingers and the fingernails.
"Something worth pointing out is herpes can cause severe infections in newborn babies, throughout their lungs, liver and even the brain. It is rare and usually, in those settings, a newborn baby has picked up the infection from the mother at the time of birth and doesn't have a good immune system to fight it," Jones said.
"It can also occur in adults, usually in the situation where someone has had cold sores previously but in this instance their immune system has been altered, so for example if someone is having cancer therapy or an organ transplant or even HIV Aids, something that would make your immune system very low."
Jones stresses these cases are very rare and, "for most of us, we can live with the virus. It can cause break outs or you might not even know herpes is being shed from skin."
Also, the good news is cold sores very rarely move from location to location. In other words, if you always get cold sores near your mouth, you're not very likely to have one crop up in your nose or eye.
"It would be highly unlikely for it to pop up somewhere else," Jones said. "Unless you got reinfected from someone else or even yourself. For example, if you touched your cold sore and then rubbed your eyes, there is the possibility you have passed the virus from one location to the other."
"The best thing do with prevention is to avoid contact with someone who has a lesion," Jones said.
"I'm talking direct contact -- you can still be in the same room as them and sit beside them -- but things like using barrier protection for sexual intercourse if someone has genital herpes; and if someone gets oral herpes, then avoiding sharing spoons or things where the virus can be shared.
"You also want to avoid kissing if they [have a cold sore] around the lips, especially babies if you have [a cold sore] yourself.
"Wash your hands with soap and water -- it doesn't have to be an alcohol rub or bacterial soap -- and try to avoid touching those lesions and even covering them if necessary."
Jones also advises people to be aware of what triggers outbreaks (sunburn and wind are some examples) and to act accordingly.
"In terms of when you have the infection, by the time it breaks out in the cold sore, you can use topical antiviral agents, though they are not particularly effective in limiting its course," Jones said.
"It's very hard for them to penetrate into where the virus is residing.
"An oral agent can help, but for most people, by the time gets it into the system, it's already too late to prevent the lesion from occurring.
"Sometimes people get tingling beforehand and they know they are doing to get something in the area -- if that's the case, that's the best time to take antiviral medication.
"If someone has really troublesome legions, or if their immune system is altered, they can get oral anti viral agents to use [more consistently], but this is only for extreme cases."
Basically, if you have a cold sore, it's already too late to pursue an effective means of treatment.
"Once it has erupted, you're less likely to be able to do anything to alter its course or lessen the duration," Jones said.
"It's a tricky virus for a couple of reasons. It gets into the body and hides in our nerves, so it's very hard to make a vaccine against, even though we've been trying for years.
"It's very difficult, because by the time the virus is showing up as a cold sore, it's quite hard to... you can't give medicine that can clear the storehouse of the virus
"You can provide some systematic relief but it won't get rid of it altogether."
A final word
Cold sores are annoying, yes, painful, yes, and can prove to be an eyesore if you happen to get a particularly bad one on your face. But, for the most part, they are an inconvenience at worst.
"For most people, you don't need any therapy. They're a nuisance, but generally a cold sore will run its course," Jones said. "You don't need antiviral agents.
"Newborn babies are the one example where they really need to be assessed and even in hospital because they usually require antiviral agents though a drip.
"Most of us, however, won't have any problems."