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What Is It?

Chlamydia (pronounced: kluh-MID-ee-uh) is a sexually transmitted disease (STD) caused by bacteria called Chlamydia trachomatis. Although you may not be familiar with its name, chlamydia is one of the most common STDs. Because there often aren't any symptoms, though, lots of people can have chlamydia and not know it.

The bacteria can move from one person to another through vaginal, oral, or anal sex. If someone touches body fluids that contain the bacteria and then touches his or her eye, a chlamydial eye infection (chlamydial conjunctivitis) is possible.

Chlamydia also can be passed from a mother to her baby while the baby is being delivered. This can cause pneumonia and conjunctivitis, which can become very serious for the baby if it's not treated. You can't catch chlamydia from a towel, doorknob, or toilet seat.

How Does a Girl Know She Has It?

It can be difficult for a girl to know whether she has chlamydia because most girls don't have any symptoms. Because of this, it's very important to see a doctor and get tested for chlamydia at least once a year if you are having vaginal, oral, or anal sex. Your doctor can tell you about how to test for chlamydia, even if you don't have any symptoms.

Much less often, a girl can have symptoms, such as an unusual vaginal discharge or pain during urination (peeing). Some girls with chlamydia also have pain in their lower abdomens, pain during sexual intercourse, or bleeding between menstrual periods.

How Does a Guy Know He Has It?

It also can be difficult for guys to know if they have chlamydia. Many who do have it will have few or no symptoms, so any guy who is having vaginal, oral, or anal sex should be tested by a doctor at least once a year.

When symptoms are there, guys may have a discharge from the tip of the penis (the urethra — where urine comes out), or itching or burning sensations around the penis. Rarely, one of the testicles may become swollen.

When Do Symptoms Appear?

Someone who has chlamydia may see symptoms a week later. In some people, the symptoms take up to 3 weeks to appear, and many people never develop any symptoms.

What Can Happen?

If left untreated in girls, chlamydia can cause an infection of the urethra (where urine comes out) and inflammation (swelling and soreness caused by the infection) of the cervix. It can also lead to pelvic inflammatory disease (PID), which is an infection of the uterus, ovaries, and/or fallopian tubes. PID can cause infertility and ectopic (tubal) pregnancies later in life.

If left untreated in guys, chlamydia can cause swelling and irritation of the urethra and epididymis (the structure attached to the testicle that helps transport sperm).

How Is It Treated?

If you think you may have chlamydia — or if you have had vaginal, oral, or anal sex with a partner who may have chlamydia  you need to see your family doctor, adolescent doctor, or gynecologist. Some local health clinics, such as Planned Parenthood, also can test and treat people for chlamydia. It's now routine for doctors to check all teens 15 years of age and up for chlamydia, regardless of whether they say they're having sex — this is to make sure that everyone who needs treatment gets it.

Doctors usually diagnose chlamydia by testing a person's urine. If you have been exposed to chlamydia or are diagnosed with chlamydia, the doctor will prescribe antibiotics, which should clear up the infection in 7 to 10 days.

Anyone with whom you've had sex will also need to be tested and treated for chlamydia because that person may be infected but not have any symptoms. This includes any sexual partners in the last 2 months or your last sexual partner if it has been more than 2 months since your last sexual experience. It's very important for people diagnosed with chlamydia to abstain from having sex until they and their partner have been treated.

If a sexual partner has chlamydia, quick treatment will reduce his or her risk of complications and will lower your chances of being reinfected if you have sex with that partner again. (You can become infected with chlamydia again even after you have been treated — having chlamydia once does not make you immune to it.)

It's better to prevent chlamydia than to treat it, and the best way to prevent the infection is to abstain from all types of sexual intercourse. If you do have sex, use a latex condom every time. This is the only birth control method that will help prevent chlamydia.

Date reviewed: January 2016