Lots of people get cold sores, they're nothing to panic about. Still, they're probably not your favourite thing...

Don't pick, the cold sore will last longer.

How do I know if I've got a cold sore?

You'll get a tingle on or around your lips, then a little blister (a fluid-filled blob). Then a sore patch after the blister bursts and oozes, then a crust. Nice. But thankfully, they are almost always gone within a week or so.

What causes them?

Herpes. Cold sores are caused by a virus called Herpes Simplex Virus (HSV) - the same virus that can give us genital herpes.

Cold sores on the privates are unpleasant. And sexually transmitted. But cold sores on the mouth are less of a problem. 1 in 5 people get them and it's nothing to do with sex.

How do I get them?

HSV is very contagious. The first time we get cold sores (usually when we're still a kid) it's from kissing someone who has one. So thanks, Mum/Gran/Auntie Janice. If cold sores come back, we haven't caught HSV again. It's our own HSV causing the trouble - HSV sleeps in our bodies, ready to wake up again from time to time.

How do I stop cold sores coming back?

Sometimes it's impossible to keep the HSV sleeping. And for 20% of us, the cold sores come back over and over again.

But here's a list of common culprits:

  • Injury to the affected area
  • Stress
  • Being run down/tiredness
  • Periods (sorry ladies!)

I have a cold sore! Help!

Don't pick, the cold sore will last longer. Take some paracetamol - those bad boys can hurt, and get some cold sore cream from the chemist (ask your pharmacist). The sooner you get that on the better, so don't wait until the crust stage.

If you have cold sores that won't go away, are anywhere other than your lips, or your eyes start itching and/or going red, head to your GP.

BBC Advice factfiles are here to help young people with a broad range of issues. They're based on advice from medical professionals, government bodies, charities and other relevant groups. Follow the links for more advice from these organisations.