Sexually transmitted diseases (STDs) are diseases that are mainly passed from one person to another during sex. There are at least 25 different sexually transmitted diseases with a range of different symptoms. These diseases may be spread through vaginal, anal and oral sex.

Most sexually transmitted diseases will only affect you if you have sexual contact with someone who has an STD. However there are some infections, for example scabies, which are referred to as STDs because they are most commonly transmitted sexually, but which can also be passed on in other ways.

Sexually transmitted infection (STI) is another name for sexually transmitted disease (STD). The name STI is often preferred because there are a few STDs, such as chlamydia, that can infect a person without causing any actual disease (i.e. unpleasant symptoms). Someone without symptoms may not think of themselves as having a disease, but they may still have an infection that needs treating.

How to tell if you have an STD

You may become aware that you have an STD because of symptoms, or it may be that a sexual partner tells you they have an STD which they might have passed on to you. Some sexually transmitted diseases can be transmitted by an infected person even if they don’t have any symptoms. Certain STDs can also be transmitted from a pregnant woman to her unborn child.

If you think you might have been exposed to an STD then you should go to see a doctor. Many sexually transmitted diseases can be easily cured, but if left untreated, they may cause unpleasant symptoms and could lead to long-term damage such as infertility. It is important that anyone diagnosed with an STD informs everyone they have had sex with within the past year (or everyone following the partner they believe may have infected them).


Bacterial Vaginosis

BV is caused by an imbalance in the normal healthy bacteria found in the vagina. Although it is relatively harmless and may pass unnoticed, it can sometimes produce an abundance of unpleasant fishy smelling discharge.

BV is not strictly an STD as it is not transmitted via sexual intercourse. However, it can be exacerbated by sex and is more frequently found in sexually active women than those who have never had intercourse.

A woman cannot pass BV to a man, but it is important she receives treatment as BV can occasionally travel up into the uterus and fallopian tubes and cause a more serious infection. Treatment for BV consists of applying a cream to the vagina or taking antibiotics.


Chlamydia is one of the most commonly reported bacterial sexually transmitted diseases. It is caused by the chlamydia trachomatis bacterium. It infects the urethra, rectum and eyes in both sexes, and the cervix in women. If left untreated, long-term infection can lead to fertility problems in women. Chlamydia is transmitted through genital contact and/or sexual intercourse with someone already infected. Symptoms of chlamydia usually show between 1 and 3 weeks after exposure but may not emerge until much later.

Crabs or Pubic Lice

Crabs or pubic lice are small crab-shaped parasites that burrow into the skin to feed on blood. They live on coarse body hair, predominantly pubic hair, but can also be found in armpit hair, facial hair and even on eyelashes. The lice are yellow-grey in colour and use their crab-like claws to grip hair strands. They can sometimes be spotted moving on the skin.

Crabs are easily passed on during sex, but can also be passed on through sharing clothes, towels or bedding with someone who has them. Crabs cannot be transmitted via toilet seats or swimming pools.

Symptoms of crabs are usually noticed around 5 days to 7 weeks after infection and include:

  • itchy skin
  • sometimes visible lice and eggs
  • spots of blood as lice feed from blood vessels in the skin

Although there is no effective way to prevent becoming infected during sex, a person who has crabs can reduce the risk to others by washing bedding, towels and clothes on a hot wash to kill off the parasites.

Treatment for public lice is easy, consisting of special shampoos, lotions and creams that kill the lice and their eggs. It is not necessary to shave pubic hair as this is unlikely to remove all lice.

Genital warts

Genital warts are caused by some sub-types of human papilloma virus (HPV). They can appear on the skin anywhere in the genital area as small whitish or flesh-coloured bumps, or larger, fleshy, cauliflower-like lumps. They are unlikely to cause pain but may itch and can be difficult to spot. Often there are no other symptoms of genital warts, but if a woman has a wart on her cervix she may experience slight bleeding or unusual coloured vaginal discharge.


Gonorrhea is a sexually transmitted infection that can infect the urethra, cervix, rectum, anus and throat. Symptoms of gonorrhea usually appear between 1 and 14 days after exposure, but it is possible to have no symptoms. Men are more likely to notice symptoms than women. Symptoms can include:

  • a burning sensation when urinating
  • a white/yellow discharge from the penis
  • a change in vaginal discharge;
  • irritation or discharge from the anus (if the rectum is infected)


Herpes is caused by two strains of the herpes simplex virus, type 1 (HSV-1) and type 2 (HSV-2). HSV-2 is more common and usually manifests itself in the genital and anal area, whereas HSV-1 is more likely to affect the mouth and lips in the form of cold sores. On a global scale, HSV-2 is a very common STD. Symptoms of herpes usually appear 2 to 7 days after first exposure to the virus and last 2 to 4 weeks. Both men and women may have multiple symptoms, including:

  • itching or tingling sensations in the genital or anal area
  • small fluid-filled blisters that burst leaving small painful sores
  • pain when passing urine over the open sores (especially in women)
  • flu-like symptoms, including swollen glands or fever

Once the first outbreak of blisters has gone, the herpes virus hides away in nerve fibres near the infection site, where it remains dormant, causing no symptoms. Symptoms may come back later (particularly during times of stress and illness) but usually in less severe and shorter episodes. Read more about herpes.