Sexually Transmitted Infections

Sexually transmitted infections (STIs)

Sexually transmitted infections (STIs) are diseases passed on from one person to another through unprotected sex (sex without a condom) or sometimes through genital contact.

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

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


Chlamydia is one of the most common STIs in the UK. Most people who have chlamydia don’t notice any symptoms and won’t know they have the infection. Otherwise, symptoms may include pain when you urinate, unusual discharge and, in women, bleeding between periods or after sex.

Diagnosing chlamydia is easily done with a urine test or a swab of the affected area. Chlamydia is easily treated with antibiotics, but can lead to serious long-term health problems if it's left untreated. 

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 are the result of a viral skin infection caused by the human papillomavirus (HPV).

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, such as creams and cryotherapy (freezing the warts).

Read more about genital warts

Genital herpes

Genital herpes is a long-term condition caused by the herpes simplex virus (HSV).

After you have become infected, the virus remains dormant (inactive) for most of the time. There are often few or no initial symptoms. However, certain triggers can activate the virus, causing outbreaks of painful blisters on your genitals and the surrounding areas.

There's no cure for genital herpes, but the symptoms can usually be effectively controlled using antiviral medicines. 

Read more about genital herpes.


Gonorrhoea is a bacterial infection that can cause an unusual discharge from your vagina or penis, and pain when urinating.

Gonorrhoea can be easily diagnosed through a simple swab test and treated with antibiotics. If left untreated, it can lead to more serious long-term health problems and infertility.

Read more about gonorrhoea.


Syphilis is a bacterial infection that causes a painless but highly infectious sore on your genitals or sometimes around the mouth. The sore lasts two to six weeks before disappearing. 

Secondary symptoms, such as a skin rash and sore throat, then develop. These may disappear within a few weeks, after which you have a symptom-free phase.

If diagnosed early, syphilis can be easily treated with antibiotics, usually penicillin injections. But if it is left to progress untreated, syphilis can go on to cause serious conditions such as stroke, paralysis, blindness or death.

Read more about syphilis.


HIV is a virus most commonly caught by having unprotected sex or sharing infected needles to inject drugs.

The virus weakens your ability to fight infections and cancer. AIDS is the final stage of HIV infection, when your body can no longer fight life-threatening infections. There's no cure for HIV but there are treatments to enable most people with the virus to live a long and healthy life.

Read more about HIV and AIDS and Coping with a positive HIV test.


Trichomoniasis is a condition caused by a tiny parasite called Trichomonas vaginalis.

Women may have soreness and itching around the vagina and a change in vaginal discharge. Men may experience pain after urination and ejaculation.

Most men and women are treated with an antibiotic called metronidazole, which is very effective.

Read more about trichomoniasis.

Pubic lice

Pubic lice ('crabs') are tiny blood-sucking insects that live in coarse human body hair, most commonly pubic hair. They cause itching and red spots.

They can usually be successfully treated with insecticide medicines available over the counter in most pharmacies, or from a GP or GUM clinic.

Read more about pubic lice.


Scabies is a contagious skin condition in which the main symptom is intense itching. It's caused by tiny mites that burrow into the skin.

Scabies isn't only spread through sexual contact, but also through skin-to-skin contact for long periods of time with someone who is infected.

It's treated with cream containing insecticides, which kills the scabies mite.