The lowdown on sexually transmitted infections (STIs)

Written by: Dr Nneka Nwokolo
Edited by: Top Doctors®

Sexually transmitted infections (STIs) are passed on during sex. Using condoms prevents most STIs, but some, such as herpes and HPV, aren’t completely prevented by using condoms because they may be present on skin not covered by a condom.

Most common STIs

  • Chlamydia – is the commonest bacterial STI, which affects both men and women. In women it may cause bleeding after sex, increased vaginal discharge, discomfort passing urine and lower abdominal or pelvic pain. It may also cause infertility. Often, it causes no symptoms so people don’t know they have it. In men, it may cause a discharge from the urethra (water passage), discomfort passing urine or swelling of the testicles.
  • Mycoplasma – in men, this infection may cause a urethral discharge and in women may be a cause of pelvic pain.
  • Gonorrhoea – causes symptoms very similar to chlamydia.
  • Trichomoniasis – is caused by a parasite and is more common in women than men. It causes a frothy, greenish, intensely itchy vaginal discharge, often with a bad smell.
  • Syphilis – this infection is becoming more common. It starts with a painless (sometimes painful) sore in the genital area, followed by an allover body rash. Sometimes there are no symptoms. Syphilis may be transmitted from a mother to her unborn child so women are tested for it in pregnancy.
  • Herpes – the same virus that causes oral cold sores (herpes simplex) also causes genital herpes. It causes painful blisters on the genitals and the first time it occurs may cause flu-like symptoms. As with cold sores, symptoms can recur from time to time. Very often, a person can have herpes without any symptoms and give it to another person without knowing it.
  • HPV – Human Papillomaviruses are a group of viruses that cause common hand warts, veruccas and genital warts. HPV is also the cause of cervical and anal cancer. There are now vaccines against HPV, which have already been shown to reduce the incidence of genital warts and cervical cancer.
  • HIV - Human Immunodeficiency Virus is a virus that weakens the immune system. People may suffer from infections that would be unusual in someone with a normally functioning immune system. HIV is no longer a fatal disease and, with treatment, most people have a normal life expectancy. Best of all, people on treatment aren’t infectious so can’t transmit the virus to anyone else. Pregnant women are tested for HIV in pregnancy so that if necessary, they can be started on treatment to prevent transmission to their babies.
  • Hepatitis B and C - these viruses infect the liver and if untreated, may cause liver damage (cirrhosis) and liver cancer. People often have these infections without knowing it, but in some people they cause jaundice (yellowing of the skin and whites of the eyes). Vaccination against hepatitis B prevents people from catching it. There is no vaccine against hepatitis C.

How often should I get tested?

Tests are recommended if you have any symptoms, or any concerns about a possible risk. It’s a good idea to have tests at the beginning and end of a relationship and encourage partners to do the same.

How are STIs treated?

Most STIs can be treated with antibiotics or antivirals depending on the cause. Some STIs, like HPV, have no cure but their effects can be treated.

What happens if I ignore symptoms?

If symptoms are ignored, complications may result. For example, untreated chlamydia and gonorrhoea may cause blockage of the tubes carrying eggs from the ovaries to the uterus (fallopian tubes), which may lead to infertility.

How are tests done?

If you have no symptoms, most tests can be done without an examination. Women can take their own vaginal swabs and men usually only need to give a urine sample. Men who have sex with men are able to take their own throat and rectal swabs. Tests for HIV, syphilis and hepatitis B and C are done by a blood test. People with symptoms should see a doctor or nurse so that the right tests can be done.

Dr Nneka Nwokolo

By Dr Nneka Nwokolo
Genitourinary Medicine

Dr Nneka Nwokolo is a London based consultant physician in Sexual Health and HIV Medicine who is known for her sensitivity and discretion.

Dr Nwokolo has extensive experience in the management of sexually transmitted infections STIs and HIV in men and women, and a special interest in the management of chronic and recurrent problems such as genital herpes, recurrent thrush and bacterial vaginosis. She has particular expertise in the treatment of syphilis and antibiotic-resistant gonorrhoea.

Other areas of expertise include contraception, management of the menopause, the sexual health of women and adolescents and pre and post-exposure prophylaxis against HIV infection.

She was the lead author of the 2015 UK National Guideline for the Management of Genital Chlamydia Infection. She has many publications in the fields of sexual health and HIV.

Dr Nwokolo provides the full range of contraceptive methods including implants and intrauterine contraception and is an instructing doctor for the Faculty of Sexual and Reproductive Health, providing training in contraception to doctors and nurses. She is the lead for young people in her NHS practice and provides sympathetic sexual health care and contraception to adolescents over the age of 16.


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