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Sexually transmitted infections (STIs)

Sexually transmitted infections (STIs) pass from one person to another through unprotected vaginal, anal or oral sex, by genital contact and through sharing sex toys.

STIs are most common in people under 25, but anyone who is sexually active is at risk. The most common STI is chlamydia, followed by genital warts.

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  • Symptoms Symptoms of sexually transmitted infections

    If you have an STI you may have no symptoms, but there are some to look out for. These can include:

    • unusual discharge from your vagina, penis or anus
    • pain or burning when you pass urine
    • itches, rashes, lumps or blisters around your genitals or anus
    • pain and/or bleeding during or after sex
    • bleeding between periods
    • pain in your testicles
    • pain in your lower abdomen (tummy)

    It's important to be tested if you think you may have an STI. If you aren’t treated, some STIs can lead to more serious health problems, such as infertility.

  • Diagnosis Diagnosis of sexually transmitted infections

    If you think you have an STI, see your GP or go to a sexual health clinic. You don’t have to ask for a referral from your GP to go to a sexual health clinic – you can make your own appointment. All visits are confidential and you don't have to give your real name. Details won't be sent to your GP without your consent.

    To diagnose an STI, your doctor will usually need to carry out a physical examination to look for any signs of infection. For women this may include an internal examination (an examination of the vagina and cervix).

    For both men and women, tests for STIs include swabs (these are samples taken with a small, round cotton bud), and blood or urine tests.

    If you're diagnosed with an STI, it's important to contact your previous partners to prevent the spread of infection. Clinics can send anonymous notifications on your behalf if you're willing to provide details.

  • Causes Causes of sexually transmitted infections

    STIs are caused by bacteria and viruses. These infections can be passed from one person to another during intimate physical contact such as sex, genital contact, sharing sex toys and oral sex.

  • Private GP appointments

    With our GP services, we aim to give you an appointment the next day or sooner if it’s urgent. Find out more today.

  • Prevention Prevention of sexually transmitted infections

    There are measures you can take to reduce your risk of catching an STI. Safer sex methods include using condoms for vaginal, anal and oral sex and when sharing sex toys. This can help prevent the spread of HIV and reduce the risk of many STIs.

    Before having sex with a new partner, you could both consider being checked for STIs.

    If you think you're at risk of catching an STI because of your sexual activity, consider having a check-up at a sexual health clinic every few months. Once diagnosed with an STI, it's important to wait until you have been given the 'all clear' before you have sex again.

  • Types of sexually transmitted infections Types of sexually transmitted infections

    This section gives details about some of the most common STIs.


    The most common STI in the UK is chlamydia. The infection is caused by bacteria that can infect your cervix (the neck of your womb), urethra (the tube that carries urine from your bladder and out through your penis or vulva), rectum (back passage), throat or eyes.

    About seven in 10 women and half of men infected with chlamydia don’t have any signs or symptoms.

    Possible symptoms in women can include:

    • bleeding between periods or heavier periods
    • pain and/or bleeding during or after sex
    • lower abdominal pain
    • unusual vaginal discharge – such as a change in colour, texture or smell
    • pain when passing urine

    Symptoms in men can include:

    • a white, cloudy or watery discharge from the penis
    • pain when passing urine
    • pain in the testicles

    If you have a chlamydia infection in your rectum, you are unlikely to have symptoms but may notice an unusual discharge from your anus and you may have pain there. Chlamydia can be treated with antibiotics. This may either be a single dose of an antibiotic or a course of antibiotics. If you have signs and symptoms of chlamydia, your doctor may give you treatment before your test results are back.

    Genital warts

    Genital warts, the second most common STI in the UK, are caused by infection with human papilloma virus (HPV). HPV infection can cause warts on your genitals and anal area. Genital warts can also grow inside your urethra, vagina and anus. Warts can vary in appearance. They can be small, smooth, round bumps, larger growths that are grouped together, or small cauliflower-shaped bumps.

    You can have HPV without having any symptoms, and you can pass on the virus even when you don’t have any signs of genital warts. Using a condom reduces the chances of passing on the virus but, as the infected areas of skin might not be covered by a condom, this may not fully protect you or your partner against genital warts. Warts can start to appear weeks, months or years after coming into contact with the virus.

    Although the warts may disappear on their own, treatments include a chemical solution, cream or liquid nitrogen (cryotherapy). Surgical removal is also an option. You may need to have repeat treatments to get rid of the warts.

    Genital herpes

    Genital herpes is caused by the herpes simplex virus (HSV). Many people infected by this virus won’t have any symptoms.

    If you do have symptoms, you may first notice stinging, tingling or itching in the genital or anal area followed by the development of fluid-filled blisters or sores on your genitals, anal area or tops of your thighs. You may also feel generally unwell, tired or have a fever.

    The blisters will heal within about three weeks, but after the first ‘primary’ episode of genital herpes, you may have further outbreaks in the following months. These recurrent outbreaks tend not to last as long or be as severe.

    Another type of the virus causes oral herpes (cold sores). These can be passed to the genitals during oral sex. Genital herpes can also be passed to the mouth by oral sex.

    You can have the virus but not have any symptoms and still pass the virus on to your partner. Using condoms can help to reduce the chances of passing the virus on, but can’t completely prevent this happening.

    There is no treatment that can completely remove the herpes simplex virus from your body, but your doctor can prescribe antiviral medicine to help clear up the blisters more quickly. You can help to manage your symptoms by having salt baths and taking painkillers.


    Gonorrhoea is caused by bacteria that can infect your urethra, cervix, rectum, mouth and throat. You may have symptoms that appear 10 or more days after you become infected. However, one in 10 men and half of all women who are infected have no symptoms.

    In women, symptoms may include:

    • unusual vaginal discharge, which may be yellow or green
    • pain when passing urine
    • lower abdominal pain or tenderness (this is rare)
    • rarely, bleeding between periods or heavier periods

    In men, symptoms may include:

    • unusual discharge from the tip of the penis, which may be white, yellow or green
    • pain when passing urine
    • pain or tenderness in the testicles
    • inflammation of the foreskin (this is less common)

    You may sometimes have other symptoms depending on where the infection is. If it’s in your rectum, usually there aren’t any symptoms but you may have anal pain, discomfort or discharge. Gonorrhoea infection, as a result of oral sex, can occasionally cause a sore throat.

    It’s important to be treated for gonorrhoea as the infection can cause serious long-term health problems including infertility. Gonorrhoea can be treated with antibiotics.

    Hepatitis B

    Hepatitis B virus causes hepatitis, which is an inflammation of your liver. About half of people with hepatitis B have symptoms, which start about one to six months after you become infected.

    Symptoms can include:

    • feeling generally unwell with a sore throat, tiredness, joint pains and a loss of appetite
    • feeling sick or vomiting
    • abdominal pain
    • yellowing of your skin and eyes (jaundice)
    • itchy skin
    • darker urine

    Most people will recover from hepatitis B without treatment, but if you don’t clear the infection after six months, you will become a chronic carrier of the disease. Being a chronic carrier means you may have no symptoms and be unaware that you’re infected, but you may still pass the infection on to other people.

    A chronic illness is one that lasts a long time, sometimes for the rest of the affected person’s life. When describing an illness, the term ‘chronic’ refers to how long a person has it, not to how serious a condition is. Being a chronic carrier means you will be at a greater risk of developing cirrhosis of the liver and liver cancer.

    Initial treatment for hepatitis B usually involves managing the symptoms with painkillers and anti-sickness medicines. If you go on to develop chronic hepatitis B, you will be referred to a specialist who may recommend antiviral medicines.

    A vaccine is also available to prevent hepatitis B, and is recommended for people who are at risk, such as those who change sexual partners frequently, particularly men who have sex with men.

    If you haven’t been vaccinated against hepatitis B and have been exposed to the virus through sexual contact with someone who has the virus, you can be given an injection (hepatitis B immunoglobulin) and an accelerated course of the vaccine. You can get this treatment at a sexual health clinic. It works best if you are given it within 48 hours of exposure.


    Human immunodeficiency virus (HIV) affects your immune system. Some people infected with HIV have no signs and symptoms at all. But between seven and nine out of 10 people who become infected with HIV have flu-like symptoms after becoming infected. Symptoms at this stage are flu-like symptoms, such as fever, sore throat and swollen glands. Over time, the virus weakens the immune system putting you at risk of other types of infection and tumours.

    There is currently no treatment that can get rid of HIV from your body. However, at specialist centres, you can be given a combination of antiretroviral medicines to reduce the level of HIV in your blood. These treatments are very effective and work best if started sooner rather than later.

    It’s important to be treated for HIV to reduce your risk of having serious health complications later on. Even if you’re taking antiretroviral medicines for HIV, you can still pass on the infection through unprotected sex.

    If you have had unprotected sex with someone who has HIV or is at high risk of having HIV, you can take a course of antiretroviral medicines (this is called post-exposure prophylaxis). This reduces the chances of developing the infection. These work best if started as soon as possible, and must start within 72 hours of exposure to the virus. Accident and emergency departments and sexual health clinics are the best places to get post-exposure prophylaxis.

    Pubic lice

    Pubic lice (also known as crabs) are tiny insects that live in coarse body hair such as pubic hair but also chest and leg hair, beards, eyelashes and eyebrows. They are not the same as head lice.

    You may notice the lice in your body hair, but they are very tiny and hard to see. Other signs include finding the brown eggs (nits) stuck to your body hair, or seeing black powdery spots in your underwear from the lice droppings. Pubic lice may make you itch.

    You can treat a pubic lice infection with lotions or shampoos. You may need to use these over your whole body and leave on for up to 12 hours.


    Syphilis is caused by bacteria. It is not common in the UK. The disease has three stages: primary, secondary and tertiary. The primary stage begins any time between nine and 90 days after you are infected, when one or more sores may appear. These develop at the site of infection, for example your penis, anus, in your vagina or rectum, in your mouth or on your lips.

    The secondary stage begins a few weeks after the sores have healed, which takes 3 to 6 weeks. You may have symptoms including feeling generally unwell with flu-like symptoms and a rash. If you aren’t treated for syphilis, after a number of years you can develop the tertiary stage of the disease. This can cause serious health problems including problems with the nervous system and heart.

    Syphilis can be treated with antibiotics.

  • FAQs FAQs

    Are the tests for sexually transmitted infections painful?


    Not usually, although you may feel a little discomfort.


    Swabs (a small, round cotton bud used to take samples) may be taken from the penis in men and the urethra (where you pass urine) in women. Afterwards you may feel a slight discomfort when you pass urine, but this will go away. Swabs are also taken from the vagina and cervix (the neck of your womb) in women and are similar to those taken during a smear test. Finally, swabs might also be taken from your rectum if you had anal sex. Again, you may feel uncomfortable, but this shouldn’t be painful.

    You will probably be asked to have a blood test and you may be asked to provide a sample of urine.

    I'm too embarrassed to go to a sexual health clinic. Are there home-testing kits available?


    It’s possible to get home-testing kits for some STIs, but not all of them will be accurate. This could mean you get a positive result when you aren’t infected, or a negative result when you actually do have an STI. To be sure, it’s better to go to a sexual health clinic so that you can be treated quickly and find out more about preventing future STIs.


    Sexual health clinics offer free and confidential testing for STIs and advice about prevention of STIs. Although you may feel embarrassed about going to a clinic, the people who work there are used to dealing with this. Your tests will be kept confidential and you don’t have to give your real name. The long-term effects of STIs can have serious health implications. For this reason, it’s better to overcome your embarrassment and find out if you need treatment so that you can remain healthy and not pass on an STI to anyone else.

    However, in many areas of the UK, free home-testing kits are available for 16 to 25 year olds to test for chlamydia. You can order a postal test kit to be delivered to you at home. You will need to take a sample at home and then send this away to a laboratory for testing. The results will then be sent to you – you can’t diagnose yourself at home.

    You should always use self-test kits carefully. Only buy tests from reputable sources, ideally with advice from a GP or other healthcare professional. Make sure it carries a CE mark and that the packaging is intact. Always follow the instructions exactly. Remember that no test can be completely reliable and if you are worried about any sexually transmitted infection, visit a GUM clinic or see your GP.

    Should I get treatment for a sexually transmitted infection if I’m pregnant?


    Yes, it’s important that you see your GP or go to a sexual health clinic. STIs can pass to your baby before, during or after birth. If you’re pregnant and have an STI, you may need to be treated for the infection to protect yourself and your baby from serious health problems.


    Depending on the STI you have been diagnosed with, the treatment will vary. This also depends on how advanced your pregnancy is because not all treatments are suitable during all stages of pregnancy. Most bacterial STIs can be treated with antibiotics, but viral STIs can be more difficult to treat.

    If you don’t get treatment for an STI before or during pregnancy, your baby’s health could be seriously affected. Some STIs could lead to your baby being born early or having a low birth weight. In the most severe circumstances, infections can lead to a miscarriage late in pregnancy.

    Your baby may need treatment when he or she is born to help prevent complications of STIs. Sometimes you may be offered a caesarean delivery to help prevent your baby becoming infected during childbirth. HIV can be passed to babies through breastfeeding.

    Speak to your GP or midwife about the best way to protect yourself and your baby if you have been diagnosed with an STI.

    Someone I had sex with has a sexually transmitted infection but I don't have any symptoms. Should I still get tested?


    Yes, it would be a good idea to get tested. You don’t always have symptoms if you have a STI. If an STI goes untreated it can lead to serious health complications.


    Sometimes you may not know that you have an STI because you won't have any symptoms. It's important to get tested so that you can get treatment if you have an STI. If you don't and you do have an infection, it may get worse and lead to complications. You could also pass it on to someone else.

    Using a condom every time you have sex can reduce the risk of getting an STI. However, not all STIs can be prevented in this way, for example genital herpes or pubic lice, because the infectious areas might not be covered by the condom.

    If you would like further confidential advice, there are helplines you can ring to get more information about your situation.

  • Resources Resources

    Further information


    • Sexually Transmitted Infections in Primary Care. Royal College of General Practitioners. 2nd ed. 2013.
    • Chlamydia - uncomplicated genital. NICE Clinical Knowledge Summaries., published May 2009
    • Number and rates of new STI diagnoses in England 2003-2012. Health Protection Agency., published June 2013
    • Help and advice. Family Planning Association., accessed 22 August 2013
    • Warts – anogenital. NICE Clinical Knowledge Summaries., published November 2012
    • HIV infection and AIDS. NICE Clinical Knowledge Summaries., published March 2010
    • Herpes simplex – genital. NICE Clinical Knowledge Summaries., published September 2012
    • Gonorrhoea. NICE Clinical Knowledge Summaries., published November 2011
    • Hepatitis B. NICE Clinical Knowledge Summaries., published August 2010
    • Early symptomatic HIV infection. eMedicine., published 13 January 2013
    • HIV infection and AIDS. NICE Clinical Knowledge Summaries., published March 2010
    • Pubic lice. NICE Clinical Knowledge Summaries., published December 2012
    • National Chlamydia Screening Programme., accessed 22 August 2013
    • Freetest., accessed 22 August 2013
    • STDs and pregnancy – CDC factsheet., published 1 August 2013
    • Self-test kits. Medicines and Healthcare products Regulatory Agency (MHRA)., published November 2012
    • Advice about buying self-test kits for sexually transmitted diseases (STDs). Medicines and Healthcare products Regulatory Agency (MHRA)., published October 2012
    • Management of HIV in Pregnancy., published 18 February 2011
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