STIs are diseases passed on through bodily fluids and none of them are very nice. Get clued-up on how to make sure you don't get one, symptoms of the most common ones and what do if you've got one.

STIs are often silent. But that doesn't mean it's not doing you harm

What are they?

STIs (sexually transmitted infections) are diseases passed on through bodily fluids like saliva, blood and sexual fluids like sperm. We get an STI by having sex (including oral sex) with someone who's infected.

All are unpleasant. And can cause lasting damage. But most are treatable. And preventable.

How can I make sure I don't get an STI?

Use a condom every time you have sex - this is the best protection we have. Condoms are little latex life savers.

Some couples go to the doctor or clinic for a check up to make sure they are free from infection before having sex without condoms. This is a sensible move, but this check up is useful, not foolproof. The results are out of date as soon as we sleep with someone new.

How will I know if I've caught an STI?

Remember that STIs are often silent. This means that you or your partner may have one and know nothing about it.

This doesn't mean you can't pass it on, and it doesn't mean it's not doing you harm inside.

The only way to be sure is to have a sexual health screen. This means seeing your GP or local sexual health clinic and having tests done to rule out infections. Sometimes this includes swabs being taken from our genitals, blood tests and/or urine tests.

Everyone who is having sex should have an STI screen from time to time. Do the decent thing and look after yourself.

The symptoms of the most common STIs are:

  • Chlamydia and gonorrhoea: Unusual discharge from the genitals (penis or vagina), pain urinating (weeing), pain in the lower abdomen. However, about 80% of women who have Chlamydia get no symptoms at all.
  • Genital warts: Flat or cauliflower-like bumps around the genitals.
  • Genital herpes: Painful blisters or ulcers on the mouth or genitals. Flu-like symptoms like headache or swollen glands.
  • Syphilis: Ulcers (which are often painless) on the genitals. Rashes, flu-like symptoms.
  • Pubic lice: Itching around the genitals, black powder found in underwear, white specks in pubic hair.

For info on HIV and Aids, see the factfile.

What if I think I might have one?

See your doctor or sexual health clinic. Most STIs can be cured with a simple course of antibiotic pills or cream. But if left untreated they can cause more serious health problems like not being able to have babies.

Remember, the professionals you meet spend all day every day screening people for STIs. People of all shapes, sizes and sexualities. No one will judge or lecture you, they'll just think you're smart for taking care of yourself.

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.