Chlamydia is a sexually transmitted infection (STI) caused by the bacteria chlamydia trachomatis. It is passed from person to person by bodily fluids (semen and vaginal fluids) during sex. Chlamydia is very contagious, meaning it is easily passed from one person to another. It can be spread through:

  • unprotected vaginal, oral, or anal sex
  • sharing sex toys without washing or covering with a new condom
  • genital to genital contact (even without penetration or ejaculation)
  • infected semen or vaginal fluids coming into contact with your eyes

If you have chlamydia while pregnant, you can pass it to your baby during childbirth.

How common is chlamydia?

Chlamydia is one of the most common STIs and is thought to affect around 1 in 10 sexually active young people in the UK. Because many people with chlamydia don’t know they have it, that figure may be much higher. Chlamydia is most common in people under 25 years of age.  

Are there different types of chlamydia?

There are 3 types of chlamydia bacteria that cause infection in humans. 

  • Chlamydia trachomatis affects the genitals, eyes, and rectum. It can also cause pneumonia in babies born to infected mothers. 
  • Chlamydia pneumoniae and Chlamydia psittaci cause respiratory infections like pneumonia. 

Chlamydia trachomatis can cause infection in the genitals or different parts of the body including the: 

  • rectum (bum). If you have unprotected anal sex. Symptoms may include pain, discomfort, and discharge from your rectum. 
  • eyes. If semen or vaginal fluids come into contact with the eyes it can cause an infection known as conjunctivitis
  • throat. Chlamydia infection of the throat can occur after oral sex with an infected person. This is rare and does not usually have any symptoms, but an infected person can pass chlamydia on by giving oral sex.

What are the symptoms of chlamydia?

Up to 80% of women and 50% of men with chlamydia experience no symptoms at all. For those that do have symptoms, they are often mild and may be ignored or overlooked. 

Symptoms in women include:

  • a burning pain when you pee
  • needing to pee more often
  • yellow, strong-smelling discharge from your vagina or rectum (bottom)
  • abdominal (tummy) pain
  • bleeding after sex
  • bleeding or spotting between periods

Chlamydia symptoms in men include: 

  • burning pain when peeing
  • white, grey, cloudy, or watery discharge from your penis
  • pain, burning, or itching of the tip of the penis and urethra (the tube inside the penis) 
  • pain and swelling in the testicles
  • pain of discharge in your rectum

What are the early signs of chlamydia?

There are often no early signs of chlamydia, and it usually takes a few weeks for symptoms to develop after catching the infection. Some people don’t get symptoms until many months after they have been infected. 

How long can you have chlamydia without knowing?

Because many people with chlamydia don’t have any symptoms, it's possible to have chlamydia for months or even years without knowing. You can still pass the infection on to other people even if you don’t have symptoms. 

What does chlamydia look like?

Chlamydia doesn’t usually cause any changes in how your genitals (penis and vagina) look, and it can’t be diagnosed by sight. To get an accurate diagnosis of chlamydia, you need to have a chlamydia test. 

What does chlamydia feel like?

Often, chlamydia won’t make you feel any different at all as it can be symptomless.

But if you do get chlamydia and show symptoms, you may feel pain when you pee, stomach pain, rectal pain or discharge, pain in your genitals and bleeding (for women) after sex or between periods. 

Is chlamydia painful?

Chlamydia can cause pain or discomfort in your lower abdomen or rectum (in women) or testicles (in men). Women may also feel pain during sex and both sexes may experience a burning sensation when passing urine (peeing).  

How long does chlamydia last?

Chlamydia does not go away on its own and the infection will stay in the body until you get treatment. 

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