Sexually transmitted infections (STIs)

9 min read

Sexually transmitted infections (STIs) are passed from 1 person to another through unprotected sex or genital contact.

You can be tested for STIs at a sexual health clinic, genitourinary medicine (GUM) clinic or doctor surgery.

This page provides an overview of the different STIs and links to more information about these conditions.

Chlamydia

Chlamydia is one of the most common STIs in the UK and is easily passed on during sex. Most people don’t experience any symptoms so are unaware they are infected.

In women, chlamydia can cause pain or a burning sensation when urinating, a vaginal discharge, pain in the lower abdomen during or after sex, and bleeding during or after sex, or between

periods
. It can also cause
heavy periods
.

In men, chlamydia can cause pain or a burning sensation when urinating, a white, cloudy or watery discharge from the tip of the penis, and pain or tenderness in the testicles.

It's also possible to have a chlamydia infection in your rectum (bottom), throat or eyes.

Diagnosing chlamydia is easily done with a urine test or by taking a swab of the affected area. The infection is easily treated with antibiotics, but can lead to serious long-term health problems if left untreated, including infertility.

Read more about

chlamydia
.

Genital warts

Genital warts are small fleshy growths, bumps or skin changes that appear on or around your genital or anal area. They're caused by the

human papilloma virus
(HPV).

The warts are usually painless, but you may notice some

itching
or redness. Occasionally, they can cause bleeding.

You don't need to have penetrative sex to pass the infection on because HPV is spread by skin-to-skin contact.

Several treatments are available for genital warts, including creams and cryotherapy (freezing the warts).

Read more about

genital warts
.

Genital herpes

Genital herpes is a common infection caused by the herpes simplex virus (HSV), which is the same virus that causes cold sores.

Some people develop symptoms of HSV a few days after coming into contact with the virus. Small, painful blisters or sores usually develop, which may cause itching or tingling, or make it painful to urinate.

After you've been infected, the virus remains dormant (inactive) for most of the time. However, certain triggers can re-activate the virus, causing the blisters to develop again, although they're usually smaller and less painful.

It's easier to test for HSV if you have symptoms. Although there's no cure for genital herpes, the symptoms can usually be controlled using antiviral medicines.

Read more about

genital herpes
.

Gonorrhoea

Gonorrhoea is a bacterial STI easily passed on during sex.

About 50% of women and 10% of men don’t experience any symptoms and are unaware they’re infected.

In women, gonorrhoea can cause pain or a burning sensation when urinating, a vaginal discharge (often watery, yellow or green), pain in the lower abdomen during or after sex, and bleeding during or after sex or between periods, sometimes causing heavy periods.

In men, gonorrhoea can cause pain or a burning sensation when urinating, a white, yellow or green discharge from the tip of the penis, and pain or tenderness in the testicles.

It's also possible to have a gonorrhoea infection in your rectum, throat or eyes.

Gonorrhoea can be easily diagnosed using a urine test, or by taking a swab of the affected area. The infection is easily treated with antibiotics, but can lead to serious long-term health problems if left untreated, including infertility.

Read more about

gonorrhoea
.

Syphilis

Syphilis is a bacterial infection that in the early stages can cause a painless but highly infectious sore on your genitals or around the mouth. The sore can last for up to 6 weeks before disappearing.

Secondary symptoms such as a rash, flu-like illness or patchy

hair loss
may then develop. These may disappear within a few weeks, after which you will have a symptom-free phase.

The late or tertiary stage of syphilis usually occurs after many years and can cause serious conditions, such as heart problems, paralysis and blindness.

The symptoms of syphilis can be difficult to recognise. A simple blood test can usually be used to diagnose syphilis at any stage. It can be treated with antibiotics, usually penicillin injections. When syphilis is treated properly, the later stages can be prevented.

Read more about

syphilis
.

HIV

HIV is most commonly passed on through unprotected sex. It can also be transmitted by coming into contact with infected blood – for example, sharing needles to inject steroids or drugs.

The HIV virus attacks and weakens the immune system, making it less able to fight infections and disease. There's no cure for HIV but there are treatments that allow most people to live a long and otherwise healthy life.

AIDs is the final stage of an HIV infection, when your body can no longer fight life-threatening infections.

Most people with HIV will look and feel healthy and have no symptoms. When you first develop HIV you may experience a flu-like illness with a fever, sore throat or a rash. This is called a seroconversion illness.

A simple blood test is often used to test for an HIV infection. Some clinics may also offer a rapid test using a finger prick blood test or saliva sample.

Read more about

HIV and AIDS
and coping with a positive HIV test.

Trichomonas vaginalis

Trichomonas vaginalis (TV) is an STI caused by a tiny parasite. It can be easily passed on through sex and most people are unaware they're infected.

In women, TV can cause a frothy yellow or watery vaginal discharge, which has an unpleasant smell, soreness or itching around the vagina, and pain when passing urine.

In men, TV rarely causes symptoms. You may experience pain or burning after passing urine, a whitish discharge, or an inflamed foreskin.

TV can sometimes be difficult to diagnose and your doctor may suggest you go to a specialist clinic for a urine or swab test. Once diagnosed, TV can usually be treated with antibiotics.

Read more about

trichomonas vaginalis
.

Pubic lice

Pubic lice, also called crabs, are easily passed to others through close genital contact. They're usually found in pubic hair but can live in underarm hair, body hair, beards and occasionally eyebrows or eyelashes.

The lice crawl from hair to hair but don't jump or fly from person to person. It may take several weeks for you to notice any symptoms. Most people will experience itching, and you may notice the lice or eggs on the hairs.

Pubic lice can usually be successfully treated with special creams or shampoos available over the counter in most pharmacies, or from a doctor or GUM clinic. You don't need to shave off your pubic hair or body hair.

Read more about

pubic lice
.

Scabies

Scabies is caused by tiny mites that burrow into the skin. It can be passed on through close body or sexual contact, or from infected clothing, bedding or towels.

If you develop scabies you may have intense itching that's worse at night. The itching can be in your genital area, but it also often occurs between your fingers, on wrists and ankles, under your arms, or on your body and breasts.

You may have a rash or tiny spots. In some people, scabies can be confused with

eczema
. It's usually very difficult to see the mites.

Scabies can usually be successfully treated using special creams or shampoos available over the counter in most pharmacies, or from a doctor or GUM clinic. The itching can sometimes continue for a short period even after effective treatment.

Read more about

scabies
.

When to see a doctor

If you have any of the symptoms mentioned above, visit your doctor or local genitourinary medicine (GUM) clinic as soon as possible.

It's worth getting tested if you don't have any symptoms but are concerned you could have a

sexually transmitted infection (STI)
. You should also get tested if you have had unprotected sex with somebody and you do not know their sexual health status.

If you're sexually active and under 25 years old, you should get tested for chlamydia every year or every time you have a new partner. You can get tested in places such as pharmacies, colleges and youth centres.

See a doctor urgently if you have symptoms of an STI such as:

  • you have discharge from the vagina, penis or anus that is unusual for you
  • pain when peeing, blood in your urine or pain when having sex
  • skin growths or lumps on or around your genitals or bottom (anus)
  • a rash
  • unusual vaginal bleeding such as bleeding after sex or bleeding in between your periods
  • your anus or genitals are itchy
  • your periods have become heavy or painful
  • you have redness, blisters or sores around your genitals or anus
  • you have warts around your genitals or anus
  • you have yellowing of your eyes or skin
  • warts in your throat or your mouth
  • slight pain in your testicle or a testicular lump or swelling
  • blood in your semen
  • if you think you might have been exposed to
    HIV

Go to the emergency department if you think you may have an STI and:

  • you are pregnant
  • you have a weakened immune system
  • you have abdominal or pelvic pain
  • you have a fever
  • you're sweating, feeling very cold or shivering
  • feeling nauseous or being sick
  • you're confused, short of breath or feel your heart beating very quickly
  • you're are unable to pass urine or have hardly been for a pee all day

You should also go to the emergency department, whether you believe you have an STI or not, if you feel unwell, your symptoms are severe, you have severe abdominal pain or severe pain or swelling in your testicle.

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.