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Sexually Transmitted Infections (STIs)


You can't look at someone and tell whether or not they have a sexually transmitted infection (STI). Anyone who has ever had sex or sexual contact with another person could have one, and if they are under 25 the chances are greater.

What exactly is an STI?

Sexually transmitted infections (used to be called STDs; Sexually Transmitted Diseases) can be passed from person to person through unprotected vaginal, anal or oral sex, by genital contact and through sharing sex toys. You don't need to have lots of sexual partners to get an infection. Having sex or sexual contact once with one person can be enough for an infection to be passed on.

Types of STIs

There are roughly 25 different STIs but we're going to focus on the more common ones amongst young people. There are useful websites at the end if you want to know more.


    • Is the most common STI amongst young women and young men under 25
    • Most people don't realise they have it because they don't get any symptoms
    • Can be treated with antibiotics
    • Can cause infertility in women and men

    For more information about Testing for Chlamydia click here


    • Is caused by a virus called HPV (human papilloma virus) which lives in the skin in and around the genital area
    • Are small, fleshy lumps on and around the genital area
    • Can be removed and there are a variety of methods
    • Rarely cause any long-term health problems

    • Is caused by a virus called Herpes simplex (HSV) which lives in the skin in and around the genital and anal area (genital herpes) and also the mouth and nose (cold sores) and fingers and hand (whitlows)
    • Symptoms may not be obvious and could feel like having the flu, however others may get small, fluid-filled blisters anywhere in the genital or anal area
    • Has no cure but an anti-viral drug can help reduce the symptoms and length of time you have the infection for
    • Rarely cause any long-term health problems

    • Is caused by a bacteria, which can live in semen, pre-ejaculate (precum) and vaginal fluids
    • Often doesn't have any symptoms and so people assume they don't have it
    • Can be treated with antibiotics
    • If left untreated can cause infertility (unable to have children)

    • There are three types of hepatitis; A, B and C but they are not very common in the UK and you are very unlikely to get Hepatitis C through unprotected sex.
    • Hepatitis A is virus which causes an infection of the gut that is passed on through infected faeces (poo). It can be passed on through stimulating a partner's anus with your tongue or fingers even if their anal area looks clean.
    • Hepatitis B is a virus, which is present in body fluids such as blood, saliva, semen and vaginal fluid. It can be passed from person to person through unprotected sex.
  • HIV

    • Is a virus that damages the immune system and lives in the blood, semen, pre-ejaculate (precum), vaginal fluids or breast milk of an infected person
    • Symptoms may not be obvious and at the beginning could feel like having the flu
    • Has no cure only medication to help you live with the symptoms for the rest of your life

    Click here to see a short DVD made by students in a SW London school to raise awareness about HIV.

    If you are worried that you have been exposed to HIV within the last 72 hours you may be able to access emergency medication (PEP- Post Exposure Prophylaxis) from a GUM clinic, a sexual health clinic or an accident and emergency (A&E) department. The doctor or nurse will ask you some questions and assess whether or not the treatment will be of benefit to you.

    To speak to someone in person, call THT Direct on 0808 802 1221 for more information on PEP and where to get it.

    The only way to tell if you have HIV is to have a test. Contact a GUM clinic to talk to someone about HIV and to arrange a test if you are worried. It is better to know than not know, as you can start medication earlier if you have it, to help you live a long and healthy life.


    • Is caused by a parasite, which can live in the pubic hair, body and chest hair, and facial hair including beards and eyebrows
    • Symptoms including itching in the affected area, sky-blue spots or very tiny specks of blood on the skin, black powdery droppings from the lice in your underwear, and/ or brown eggs on pubic or other body hair
    • Can be treated with special cream, lotion or shampoo
    • There are no long term health effects

    • Is caused by a bacteria, which lives in the blood
    • Has three stages of symptoms, with the first being one or more painless sores often around the genitals and the second being a painless rash which can spread all over the body. The third stage only occurs when it is untreated after many years and can cause serious damage to major organs.
    • Can be treated with antibiotics
    • If left untreated can lead to death, but this is very rare in the UK

How are STIs passed on?

They can be passed on from one person to another during vaginal, anal and sometimes oral sex, without using a condom

Sometimes an STI can be passed on when using a condom if the virus is active on the skin or in the pubic hair (such as pubic lice) which is outside the area protected by a condom or dental dam

They can also be passed on through skin to skin genital contact, you don't need to have penetrative sex (vaginal or anal) to pass it on

If you receive oral sex from someone who has a cold sore or is just about to get one

If a person with herpes on the hand or finger touches a partner's vagina, genitals or anal area

Sharing sex toys without washing them or changing the condom first

Stimulating a partner's anus with your tongue or fingers even if their anal area looks clean without using a dental dam

How can I avoid an STI?

They are very common but you can reduce the risk of getting an STI by a number of ways:

  • using a condom if you're going to have sexual intercourse, either vaginal or anal
  • using a flavoured condom (for boys) or dental dam (for girls) if you're giving oral sex
  • avoid sharing sex toys; If you do share them, wash them or cover them with a new condom before anyone else uses them
  • making love without penetration - kiss, hug, cuddle, lick, stroke, massage, bath, dance, snog, wrestle, romp, fondle, nibble, rub, shower, play... Click here for ideas.

But don't panic, they can all be treated and the most common ones cured. Click here to find clinics that can offer you information, support and treatment.

How do I know if I have an STI?

Common signs of an infection are:

  • Itching, rashes, lumps, sores, blisters or ulcers on or around your penis or vagina
  • Pain or discomfort when you pee
  • Blood in your urine
  • Unusual discharge from your vagina or penis
  • Pain in your lower abdomen
  • Pain, discomfort or bleeding when you have sex
  • Bleeding in between periods
  • Anal pain, discomfort or discharge sometimes caused by an infection in the rectum.

Occasionally STIs affect offer areas of the body such as the throat, which usually has no symptoms, and the eyes, which can cause pain, swelling, irritation and discharge (conjunctivitis).

BUT people often don't get any symptoms!

  • Many people only find out they have an STI after having a check-up. Women especially often have no symptoms at all.

If you've had some kind of unprotected sex and think you might be at risk of having an STI go along to a GUM (sexual health or genito-urinary medicine) clinic where you can be checked out. The quicker you get treated the quicker you can stop feeling worried.

What does a test involve?

The type of test you have often depends on your symptoms. One test involves either a health professional or yourself taking a swab from the cervix or tip of the penis with something that looks like a large cotton wool bud. Other tests involve taking a blood sample or asking you to fill a small pot with urine for testing.

You'll usually be offered some counselling before a HIV test. This is to help you prepare for how you may feel and react if the test result is positive.

All sexual health clinics are completely confidential. This means the staff must keep your information private and not tell anyone about your visit. They are also friendly and they won't judge you, even if you are under 16.

What happens if my test shows I have an STI?

Most STIs are easily treatable with antibiotics. If you test positive for any STI, your clinic will encourage you to talk to your current partner and sometimes to your previous partners. This is so they can also be tested. The clinic will help you find the best way to talk to other people if you need to.

Can STIs be cured?

STIs that are caused by bacteria, such as Chlamydia and Gonorrhoea can be cured with antibiotics and will have no long term impact on your health if treated quickly.

STIs caused by viruses cannot be cured but their symptoms can sometimes be treated to make them easier to live with, such as Genital Herpes and Warts. Often once you are infected with HIV you will remain infected with the virus for the rest of your life, and will be able to pass it to someone else. There is currently no way of curing the virus or removing it from the body.

Where can I get more information and advice?

Click here to find out more about visiting a GUM clinic and to watch a short video.

For more information about STIs visit:

Family Planning Association
NHS - Choices: Sex, worth talking about
NHS - Choices: Hepatitis

For information on HIV and AIDS visit: or or

For advice and support on HIV and AIDS contact:

  • THT Direct on 0845 122 1200 or visit You can also get details of rapid testing clinics and how to obtain PEP.
  • Positively UK, a helpline answered by HIV positive people, on 020 7713 0222

Emergency Help

If you have an emergency concern for your safety call 999 to get help from the Police, Ambulance or Fire Services – they are all there for you. You can also confidentially call Childline on 0800 1111, 24 hours a day every day with any concern.

If you are concerned or worried you may be pregnant or are looking for emergency contraception take a look at our local services page to find help close to you.