Chlamydia, also known as Chlamydia infection, is a sexually transmitted infection caused by Chlamydia trachomatis, a bacterium that infects and lives within human cells, sometimes resulting in several different disease states in both men and women.1 Chlamydia most commonly affects the human genitals or eyes and is one of the most common sexually transmitted infections in the world, infecting approximately 4 to 8 million new individuals each year.2 Although chlamydia is spread primarily through sexual contact, it can also be spread from the genitals to the eyes by finger contact. Chlamydia infecting the eye, known as chlamydia conjunctivitis or trachoma, is one of the most common causes of blindness in the world. Chlamydia is easily and effectively cured by antibiotics; however, if left untreated chlamydia infections can result in serious reproductive damage as well as a number of other health problems including short and long-term consequences.

(Pap smear showing the Chlamydia trachomatis bacterium)


Signs or symptoms of chlamydia infection may not always be noticeable, but if symptoms are present, they will manifest differently depending on factors such as the gender of the infected individual as well as the site of infection. In genital infections, symptoms present differently between both sexes.

In women, chlamydia infection is known as the “Silent Epidemic” because symptoms do not appear in 70-80% of cases. The cases that are symptomatic manifest as follows:

(Characteristic white discharge in the vaginal canal of a female infected with chlamydia.)

In men, chlamydia shows symptoms of infectious urethritis (inflammation of the urethra in approximately 50% of cases. These symptoms normally include:

  • Painful or burning urination

  • Unusual penile discharge, typically lighter in color and viscosity than that for gonorrhea

  • Swollen or tender testicles

Untreated chlamydia may cause infection of the epididymis, the curved tube structure near the back of the testicles in which sperm mature. In rare cases, such as infection can result in irreversible sterility if not treated in 8 weeks.2

Chlamydia is a potential cause of prostatitis in men. The infection is also known to cause a condition known as reactive arthritis, or Reiter's syndrome, which is a combination of arthritis (inflammation of joint tissue), conjunctivitis (infectious inflammation of the inner eyelids), and urethritis (inflammation of the urethra). Reactive arthritis most common affects young men. However, women of all ages are equally susceptible to the condition. In the United States, approximately 15,000 men develop reactive arthritis from chlamydia each year and about a third of those men are permanently affected by it.

(Penile discharge from nongonococcal urethritis caused by chlamydia infection)

Chlamydia infection of the eyelids is especially dangerous, as it may result in permanent blindness if left untreated. The Chlamydia bacterium has an incubation period of five to twelve days, after which the infected individual will begin to experience symptoms similar to those of pink eye. Soon after, the infection causes a harsh roughening of the inner eyelid, known as trachoma or granular conjunctivitis, which can tear at the individual's cornea and eventually cause blindness. Symptoms may include:

  • Eye irritation

  • Unusual ocular discharge

  • Trichiasis (turned-in eyelashes)

  • Swelling of lymph nodes in front of the ears

  • Photo-sensitivity

  • Increased heart rate

  • Corneal ulcer

Early intervention is absolutely essential to avoid permanent scarring or blindness.

(Adult male with advanced blinding trachoma)

Causes and Risk Factors

Chlamydia is caused through infection by bacteria, most commonly C. trachomatis, which lives parasitically inside living human cells. It is most commonly spread via vaginal, oral, or anal sex; however, it is possible for a mother to spread chlamydia to her child during delivery, resulting in pneumonia or a serious eye infection in the newborn if left untreated. Risk factors for chlamydia are not unlike those for other sexually transmitted infections and include the following:

  • Being under the age of 24

  • Being sexually active

  • Inconsistent or absent use of a condom

  • Multiple sex partners within the last year

  • History of prior sexually transmitted infections

(Life cycle of the Chlamydia trachomatis bacterium)


The United States Centers for Disease Control and Prevention recommends chlamydia screening for the following groups of individuals:

  • Sexually active females age 25 or younger. The rate of chlamydia infection is highest in this group, so a chlamydia test is highly recommended each year and after having sex with a new partner.

  • Pregnant females. Testing during a female's first prenatal exam is recommended so as to avoid pregnancy complications or spreading the infection to the newborn.

  • Males and Females with one or more risk factors for STIs. Having one or more risk factors for a sexually transmitted infection indicates a higher rate of infection if left untreated. Getting a screening test and treating chlamydia early on will prevent further spread of the infection.

The testing and diagnosis of chlamydia is similar to screening for any other suspected sexually transmitted infection and usually includes the following:

  • A swab. For females, a physician will swab the individual's vaginal discharge for culture testing in a laboratory. For males, a physician will insert a thin swab into the end of the urethra to obtain a discharge sample. A physician may swab the anus instead if it is the suspected site of infection.

  • Urinalysis. A patient's urine sample will be analyzed in a laboratory to detect the presence of an infection.

It is recommended that individuals who have been treated for chlamydia get retested in three months to ensure the infection has been completely eradicated.


Most chlamydia infections can be treated successfully without complication, provided the individual receives regular STI screenings or seeks medical attention at the first presentation of symptoms.2


Individuals who have chlamydia are at higher risk of contracting other sexually transmitted infections including gonorrhea and HIV. Pelvic inflammatory disease (PID) may occur in females if the infection is not treated early enough. PID is an infection of the uterus and fallopian tubes that causes pelvic pain and fever. Left untreated, PID can severely damage the fallopian tubes, ovaries, uterus, and cervix. Epididymitis may occur in infected males who do not receive early enough treatment for chlamydia. The epididymis is the coiled tube located beside each testicle and is responsible for the maturation of sperm. Left untreated, epididymitis can result in fever, scrotal pain, testicular swelling, and sterilization. Prostate gland infection, or prostatitis, can also occur in males if the infection spreads to the prostate. Symptoms of prostatitis include pain after sex, fever, chills, painful urination, and lower back pain.3


Chlamydia is treated with antibiotics, usually administered orally, but sometimes intravenously if the infection is severe enough. Amoxicillin, Ofloxacin, Doxycycline, or Azithromycin. Ofloxacin or Doxycycline are also useful in treating gonorrhea. Pregnant women should not take Ofloxacin and Doxycycline; instead, Azithromycin or Erythromycin should be administered. Patients receiving treatment may receive a single dose or they may need to take the medication over a period of five to ten days. Most cases of chlamydia are resolved within one to two weeks. During this time, abstinence from sex is an absolute necessity in order to prevent further spread of the infection to others and possibly back to the original carrier if he or she infects a regular sex partner. Having had chlamydia previously or receiving treatment for it provides no immunity against reinfection in the future.3


The only certain method to prevent a chlamydia infection is abstinence from sexual activity. Since this is asking quite a lot, individuals can follow these guidelines to avoid infection:

  • Use condoms. Using a male or female (latex or polyurethane) condom during sexual contact will significantly reduce one's chances of infection.

  • Limit number of sex partners. Having sex with multiple partners greatly increases one's risk of infection by any sexually transmitted pathogen.

  • Get tested. Sexually active individuals should seek regular testing for chlamydia and all other STIs, especially after having sexual contact with a new partner.

  • Do NOT douche. While douching is becoming less common as more females become aware of the potential harm it can cause, many females do not realize that douching decreases the number of “good” bacteria present in the vagina, which help to fight incoming infections.


(A typical douche bottle. Douching is highly harmful to vagina'a natural bacterial balance and may precipitate the contraction of chlamydia.)




1) Ryan, Kenneth J., C. George Ray, and John C. Sherris. Sherris Medical Microbiology: An Introduction to Infectious Diseases. New York: McGraw-Hill, 2004. Print


2) "Statistics about Chlamydia." - N.p., n.d. Web. 24 Apr. 2014.


3) "Chlamydia."Mayo Clinic. Mayo Foundation for Medical Education and Research, n.d. Web. 13 Mar. 2014. <


Image resources


Last updated 14 May 2014.

UCSB SexInfo Copyright © 2017 University of California, Santa Barbara. All Rights Reserved.