Chlamydia causes a wide range of health problems, from painful urinary symptoms to serious reproductive damage, joint inflammation, and complications in newborns. What makes it particularly dangerous is that roughly 75% of women and 50% of men with chlamydia have no symptoms at all, meaning the infection can silently cause damage for months or years before it’s detected.
Early Symptoms in Women and Men
When chlamydia does produce noticeable symptoms, they typically appear several weeks after exposure. In women, the most common signs are abnormal vaginal discharge and a burning sensation during urination. In men, symptoms include discharge from the penis, burning while urinating, and occasionally pain or swelling in one or both testicles.
Rectal chlamydia infections, which can occur in anyone who has receptive anal sex, often cause no symptoms. When they do, expect rectal pain, discharge, and bleeding. Because so many infections are silent in every location, routine screening is the only reliable way to catch chlamydia before it causes deeper problems.
Pelvic Inflammatory Disease
The most significant consequence of untreated chlamydia in women is pelvic inflammatory disease, or PID. This happens when the bacteria travel upward from the cervix into the uterus, fallopian tubes, or ovaries. PID causes inflammation that produces scar tissue both inside and outside the fallopian tubes, eventually blocking them. A large prospective study tracking women from 2008 to 2022 found that those who tested positive for chlamydia had 1.6 times the risk of developing PID compared to those who tested negative.
PID doesn’t always announce itself dramatically. Some women experience pelvic pain, fever, or unusual bleeding, while others have symptoms mild enough to ignore. Even a “quiet” case of PID can leave behind enough scarring to affect fertility.
Infertility and Ectopic Pregnancy
The scarring from PID is the primary way chlamydia leads to infertility. When scar tissue blocks or narrows the fallopian tubes, eggs can’t travel from the ovaries to the uterus, and sperm can’t reach the egg. The same long-term study found that women with a prior chlamydia infection had 2.8 times the risk of tubal factor infertility compared to women who were never infected.
Ectopic pregnancy, where a fertilized egg implants in a fallopian tube instead of the uterus, is another serious risk. Scarred or partially blocked tubes can trap a fertilized egg in transit. Women with a history of chlamydia had roughly 1.8 times the risk of ectopic pregnancy, translating to a 30 to 90% increased risk depending on other factors. Ectopic pregnancies are medical emergencies that can cause life-threatening internal bleeding if the tube ruptures.
Epididymitis in Men
In men, untreated chlamydia most commonly causes epididymitis, an inflammation of the coiled tube at the back of the testicle where sperm mature. Symptoms include a swollen, warm, or discolored scrotum, pain that usually affects one side and comes on gradually, an urgent or frequent need to urinate, discharge from the penis, and sometimes blood in the semen or a low-grade fever.
Most cases resolve with antibiotic treatment, but epididymitis that goes untreated or keeps coming back can become chronic, meaning it persists for six weeks or more. Chronic epididymitis brings ongoing testicular discomfort that can be difficult to manage. While male infertility from chlamydia is less well-documented than female infertility, the infection can damage sperm quality and the structures that transport it.
Reactive Arthritis
Chlamydia is one of the most common infectious triggers of reactive arthritis, an inflammatory condition that develops days to weeks after the initial infection. It causes pain and swelling in the knees, ankles, or heels, along with swelling of entire toes or fingers. Persistent lower back pain that worsens at night or in the morning is another hallmark. Beyond the joints, reactive arthritis can cause red, irritated eyes, painful urination (separate from the original infection), and a rash on the palms of the hands or soles of the feet.
Reactive arthritis happens because the immune system, triggered by the chlamydia bacteria, begins attacking the body’s own tissues. It can last weeks to months, and some people experience recurring flares. This is one reason chlamydia’s effects extend well beyond the reproductive system.
Complications in Newborns
When a pregnant person has untreated chlamydia, the baby can pick up the infection during vaginal delivery through contact with infected fluid. Before routine screening of pregnant patients became standard, up to 60% of newborns born to infected mothers acquired the bacteria. Of those, about 30% developed conjunctivitis (an eye infection) and roughly 15% developed pneumonia.
Chlamydial conjunctivitis in newborns typically appears 5 to 14 days after birth. It ranges from mild redness with slight discharge to severe eyelid swelling with heavy drainage. At least half of affected newborns also carry the bacteria in their nose and throat, which is why treatment targets the whole body rather than just the eyes. Left untreated, the eye infection can cause lasting vision problems, and chlamydial pneumonia in an infant requires careful medical management.
Lymphogranuloma Venereum
A more aggressive form of chlamydia, called lymphogranuloma venereum (LGV), is caused by specific strains of the same bacterium. LGV goes beyond the surface-level infection and invades deeper tissues. In heterosexual people, it commonly causes painful, swollen lymph nodes in the groin, typically on one side, that can grow large enough to form fluid-filled masses called buboes.
In men who have sex with men, LGV most often presents as severe rectal inflammation that can mimic inflammatory bowel disease. Symptoms include bloody or mucus-filled rectal discharge, anal pain, constipation, fever, and a persistent feeling of needing to have a bowel movement. Without early treatment, LGV proctocolitis can lead to chronic rectal fistulas (abnormal tunnels between tissues) and strictures (narrowing of the rectum) that may require surgical repair. LGV can also cause oral ulcers and swollen neck lymph nodes.
Why Silent Infections Are Dangerous
The core problem with chlamydia isn’t any single symptom. It’s the fact that the majority of infected people feel perfectly fine while the bacteria quietly damage their reproductive organs, trigger immune responses, or create conditions ripe for complications down the line. A woman can carry chlamydia for months, develop mild PID she attributes to cramps, and only discover the fallout years later when she has difficulty getting pregnant. A man might not realize anything is wrong until chronic testicular pain brings him to a doctor.
Annual screening is recommended for sexually active women under 25 and for anyone with new or multiple partners. Testing is simple, usually just a urine sample or swab, and treatment with antibiotics clears the infection effectively when caught early. The damage chlamydia causes, particularly scarring in the fallopian tubes, is not reversible, which is why catching it before complications develop matters so much.