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Sexually transmitted infections (STIs)

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Sexually transmitted infections (STIs) can be passed on through unprotected vaginal, anal, or oral sex. They can also be spread by sharing sex toys.

STIs are most common in people under 25 who have been sexually active. But anyone who’s sexually active can catch one.

Types of sexually transmitted infection

Several different infections can be passed on through sex. The most common in the UK are:

  • chlamydia
  • genital warts
  • gonorrhoea
  • genital herpes
  • syphilis

Chlamydia

Chlamydia is the most common sexually transmitted infection (STI) in the UK, particularly in people under 25. Many people infected with chlamydia don’t have any signs or symptoms. If you do get symptoms, they can appear up to three weeks after you’re infected. You may have:

  • cloudy white, yellow or green discharge from your vagina, penis or bottom (anus)
  • vaginal, testicular or tummy pain
  • vaginal bleeding between periods or after sex
  • a sore throat if the infection has been passed on during oral sex (although infection in this way usually has no symptoms)
  • a burning sensation when you pee
  • pain in your anus

Prompt chlamydia treatment with antibiotics is important. If it isn’t treated, chlamydia can spread internally and lead to more serious problems, such as pelvic inflammatory disease and infertility in women.

Chlamydia can also cause a condition called lymphogranuloma venereum (LGV). This is nearly always found in men who have sex with men. LGV is caused by a certain type of chlamydia and can cause painful inflammation of your bottom (back passage, anus and rectum), a discharge, and swollen lymph glands (lymph nodes). It can potentially cause permanent rectal damage but it can be treated with antibiotics.

Genital warts

Genital warts are caused by the human papilloma virus (HPV). In the UK, children aged 12 to 13 are offered the HPV vaccine, as part of the National HPV Vaccination Programme. This protects against strains (types) of HPV that cause cervical cancer and genital warts. There’s also an HPV vaccination programme for gay, bisexual, and other men who have sex with men (age 45 and under).

Genital warts can appear on the penis, vagina or anus as:

  • small, smooth, round bumps
  • several larger bumps grouped together
  • small cauliflower-shaped bumps

The bumps may be painful, burn, or itch. It can take a three weeks to 8 months after you first get the virus for the warts to appear.

You can pass the HPV virus on even if you don’t have any warts at the time. If you use a condom, it will reduce this risk but won’t fully protect your partner.

Genital warts sometimes disappear on their own within six months. But your doctor may suggest treatment, depending on where your warts are, how much they affect you, and if you have other medical conditions. You may be able to remove them with solutions or gels you apply yourself. Or you may have cryotherapy (the warts are frozen off ), laser treatment or surgery. Treatment doesn’t always work and may have to be repeated.

Genital herpes

Genital herpes is caused by herpes simplex viruses. These can cause ulcers anywhere on your body, but usually around your mouth (cold sores) and genitals.

Many people don’t have any symptoms, but symptoms may include:

  • a burning or tingling in your vagina, penis or anus
  • fluid-filled blisters or sores that develop around your vagina, cervix, penis, or mouth if you’ve had oral sex
  • feeling tired and unwell
  • a high temperature (fever)
  • pain when you pee

This first (primary) outbreak of genital herpes can last for up to three weeks if it isn’t treated. After your first infection, you may have flare-ups in the following months or years. Once you catch herpes, you have it for life, but flare-ups usually lessen as time goes on. For most people, they do eventually stop. During a flare-up, you can take antiviral medicines to help clear it up more quickly.

You can still pass the virus on to your partner when your skin looks normal. If you use condoms, it can reduce the risk, but won’t protect your partner completely. You can also pass it on during oral sex.

Gonorrhoea

Gonorrhoea is a common bacterial STI. 9 out of 10 men with gonorrhoea have symptoms. But around half of women don’t, so can be infected and not know. If you do get symptoms, they can take up to 10 days after you’re infected to appear. Gonorrhoea symptoms include:

  • a smelly or coloured discharge from your vagina or penis
  • pain when you pee
  • mild lower tummy pain or testicular pain, usually on one side
  • anal itching, bleeding or discharge
  • a sore throat (although this isn’t common)

Gonorrhoea treatment is with antibiotics (usually an injection but sometimes tablets). Don’t have unprotected sex until both you and your partner have been tested and finished treatment at least seven days earlier. If it isn’t treated, gonorrhoea can cause serious long-term health problems including pelvic inflammatory disease and infertility in women, and painful joints (reactive arthritis).

Hepatitis

Hepatitis is a viral infection of your liver. There are three forms of hepatitis – A, B, and C – that you can catch through sexual contact or sharing contaminated needles when injecting drugs.

Most people with hepatitis B or C don’t have any symptoms. If you do have symptoms, they can begin any time from around eight weeks to six months after you’re infected. Hepatitis A may not cause symptoms, although they can appear after around six weeks and last for weeks or months.

Hepatitis symptoms include:

  • flu-like symptoms
  • sickness and vomiting
  • an ache below your ribs on your right side
  • yellowing skin and eyes (jaundice)
  • itching
  • darker pee and lighter-coloured poo
  • aching joints
  • weakness and lack of energy

Hepatitis A gets better on its own, although it can take months to get back to normal.

Although either can cause serious illness, most people with hepatitis B and some with hepatitis C get better without treatment. You’ll need regular blood tests and you may have antiviral medicines.

Acute hepatitis often goes away without antiviral treatment but some people develop chronic (long-term) hepatitis. This increases your risk of liver cirrhosis or cancer.

You can be vaccinated against hepatitis A and B if you’re at high risk. If you think you’ve been exposed to hepatitis A or B and haven’t been vaccinated, go to a sexual health clinic as soon as possible. The hepatitis B protection works best if you have it within 48 hours of being exposed to the hepatitis B virus, although you can have it for up to a week afterwards. For hepatitis A, you can have the protective injection up to two weeks after exposure.

There’s no vaccine for hepatitis C.

HIV

Human immunodeficiency virus (HIV) is a virus that can cause AIDS. HIV can be passed on during sex or through contaminated needles or syringes.

You may not have any signs and symptoms when you’re first infected with HIV. Or you may have symptoms up to six weeks afterwards, such as:

  • a high temperature (fever) and night sweats
  • a skin rash
  • aches and pains
  • a sore throat
  • headaches
  • swollen glands

Over time, the HIV virus can weaken your immune system, which increases your risk of other infections and tumours.

Treatments called antiretrovirals can control the virus. They reduce your risk of serious complications, including developing AIDS, and keep you well so you can live a long life. Effective treatment can lower the level of HIV in your blood to the point that it’s an ‘undetectable viral load’, or virally suppressed. At this point, you cannot pass on HIV through sexual contact.

There are also medicines you can take to prevent you from getting HIV. These are called pre-exposure prophylaxis (PrEP). PrEP is very effective in preventing the transmission of HIV during sex because it helps to stop HIV from entering your cells and replicating.

If you think you’ve been exposed to HIV, visit a sexual health clinic or an Accident and Emergency (A&E) department as soon as possible. You can take a course of antiretroviral medicines (post-exposure prophylaxis) to reduce your risk of infection. This works best the sooner you have it, but you can have it up to 72 hours after exposure to HIV.

Syphilis

Syphilis is a bacterial STI that has three stages: primary, secondary, and tertiary.

The primary stage begins any time between nine and 90 days after you’re infected. You usually have one ulcer on your skin, called a chancre (pronounced ‘kanker’) but you may have more. You may not notice chancres because they’re painless. They can be anywhere on your body, but most often on the penis, anus, vagina, cervix, mouth, or lips. They usually heal within six weeks.

The secondary stage usually begins around six weeks after your chancres have healed. But it may develop some months later. You may feel generally unwell with flu-like symptoms, swollen glands, and a rash.

It’s important to have syphilis treatment with antibiotics. This is usually an injection into a muscle of your buttocks. If you don’t have treatment, you may develop the tertiary stage of the disease years later. This causes serious health problems, and can affect many parts of your body including your nervous system, eyes, and heart.

Pubic lice

Pubic lice or ‘crabs’ are tiny insects that live in coarse body hair, including pubic hair, chest hair, eyelashes, and eyebrows.

Pubic lice are very hard to see. You may notice itchy red spots on your skin or brown eggs (nits) stuck to your body hair. Or you may notice brown-black (rusty-looking) powdery spots in your underwear from lice droppings.

Pubic lice treatment is with insecticide lotions or creams that you can buy in a pharmacy. You use these over your whole body, including eyebrows, beard, and other body hair, and repeat the treatment seven days later. Any sexual partners you’ve had in the previous three months need to check if they’re infected.

Trichomoniasis

Trichomoniasis is caused by a parasite called Trichomonas vaginalis (TV). You usually get trichomoniasis symptoms within a month of being infected. Women don’t always get symptoms but if you do get them, trichomoniasis symptoms include:

  • a smelly yellow or green discharge from the vagina
  • painful sex
  • itching around your vagina
  • pain in your pelvis

Men usually don’t have symptoms of trichomoniasis, but can sometimes get:

  • a discharge from the penis
  • painful testicles
  • pain when peeing, peeing a lot or cloudy pee

Trichomoniasis treatment is with antibiotics – it won’t go away without treatment. Wait until both you and any sexual partners have been treated before you have sex again.

Causes of sexually transmitted infections

STIs are caused by bacteria, viruses, or parasites. You can catch these infections during sex, by genital contact, sharing sex toys, and oral sex with an infected person.

Some blood-borne viruses can be passed on during sex, by contact with bodily fluids, or through sharing contaminated needles and syringes.

Symptoms of sexually transmitted infections

STIs vary depending on which infection you have. See the different symptoms listed under each named STI in our section on types of sexually transmitted infection.

STI symptoms also vary between people. STIs don’t always cause symptoms, so you may not realise you have one.

Even without symptoms, you can pass an STI to someone else. So, it's important to get tested if you think you’re at risk. Go to your GP or a sexual health clinic if you:

  • have had new sexual contact without using a condom or barrier contraceptive
  • are planning to have unprotected sex

Some STIs can lead to more serious health problems (including infertility) if not treated.

Diagnosis of sexually transmitted infections

If you think you’re at risk of an STI, go to a sexual health or genito-urinary medicine (GUM) clinic, or call your GP for advice. Sometimes STIs are diagnosed through tests for a urine infection or a vaginal infection.

All visits to sexual health clinics are confidential. You don’t have to give your real name and your details won’t be sent to your GP unless you agree.

They’ll usually ask about:

  • your medical history
  • whether you’ve had STI symptoms or an STI before
  • your current and recent sexual partners
  • the types of sex you have (vaginal, anal or oral, for example)
  • the type of contraception you use (if any)

You’ll usually need an examination to check for signs of infection. A doctor or nurse may examine your vagina and cervix, penis, bottom (anus), or throat. They may take swabs (samples) with a small cotton bud, blood tests, and urine (pee) tests. These shouldn’t hurt, but a swab or internal examination may be uncomfortable.

If you’re diagnosed with an STI, it’s important your previous sexual partners know, so they can be tested and treated, and don’t pass the infection on. They may not have symptoms and not realise they have an infection. If you don’t want to contact them, a GUM clinic can contact them anonymously on your behalf.

There are home self-testing kits for some STIs (for example, chlamydia) available online and from pharmacies. Some are NHS-approved and available for free, while others you pay for. It may depend on where in the UK you live, and your age. Only buy or order these tests from somewhere you trust. Because chlamydia often has no symptoms in women, pharmacies can supply free test kits to women as part of the National Chlamydia Screening Programme.

Concerned about STIs, or want to check your sexual health?

Concerned you have an STI, may have been exposed to one or just want to have a full screen, we offer a range of sexual health services.

Prevention of sexually transmitted infections

Practise safer sex to lower your risk of catching or passing on a sexually transmitted infection (STI).

  • Use condoms for vaginal, anal, and oral sex.
  • Both get tested for STIs before you and a new partner have sex.
  • Don’t share sex toys or wash them before and after anyone else uses them.
  • Get vaccinated against STIs such as HPV, hepatitis A, and hepatitis B if you’re at risk (if you’re not sure, ask your doctor or nurse).
  • Ask your doctor or sexual health clinic about tablets for preventing HIV (PrEP).

Yes, you should get tested if you've had sex with someone with an STI. STIs don’t always cause symptoms but if left untreated, could get worse or cause serious health complications. Some can lead to infertility. And if you’re infected, you could pass a STI on to someone else. Go to a sexual health or genito-urinary medicine (GUM) clinic to get a test.

For more information, see our section on diagnosis of STIs.

Yes, you can often treat (and cure) an STI. For example, bacterial STIs such as chlamydia, syphilis or gonorrhoea can be treated and cured with antibiotics. You can get rid of pubic lice with insecticide lotions or creams. Other STIs can be treated well, but the infection will remain in your body – for example, HIV and herpes. It’s important to wait until you (and any sexual partner) have completed treatment before you have sex again.

For more information, see our section on types of STI.

If you think you may have an STI, you should see a doctor – preferably at a sexual health clinic. Sexual health clinics are totally confidential and you don’t even have to give your own name. Many STIs cause similar symptoms and you really can’t get diagnosed online because you may need to have urine, blood or swab tests. It’s important to get treatment to avoid future health problems, and to avoid passing on the infection.

A sexually transmitted infection (STI) is an infection with bacteria, viruses or parasites that can be passed on through unprotected vaginal, anal or oral sex. STIs can also be spread by sharing sex toys.

For more information, see our section on types of STI.

Some STIs can’t be cured and you have them for life once infected, but there are medicines that help to control the symptoms. These are generally the viral infections such as genital herpes or HIV. You can also develop a long-lasting (chronic) infection if you catch hepatitis.

See your doctor or go to a sexual health clinic if you have an STI. Treatment can help, even if it won’t get rid of the infection completely.

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