Chlamydia causes a wide range of health problems, from painful urinary symptoms to permanent damage to the reproductive system. What makes it particularly dangerous is that it often produces no symptoms at all, allowing the infection to silently spread and cause internal harm over weeks or months. Left untreated, chlamydia can lead to infertility, chronic pain, pregnancy complications, and joint inflammation.
Why Chlamydia Often Causes Damage Before You Notice It
Most people with chlamydia have no symptoms. The bacteria can live in your genital tract, rectum, or throat without producing any obvious signs of infection. During that time, it’s still active, triggering low-level inflammation that gradually damages surrounding tissue. This is why routine screening matters so much: the CDC recommends annual testing for all sexually active women under 25, and for men who have sex with men at least once a year regardless of condom use.
When symptoms do appear, they tend to be mild enough that people dismiss them. Women may notice unusual vaginal discharge or a burning feeling when urinating. Men may have discharge from the penis, burning during urination, or pain and swelling in one testicle. Rectal infections can cause pain, discharge, and bleeding, but often cause nothing at all.
Pelvic Inflammatory Disease and Infertility in Women
The most serious consequence of untreated chlamydia in women is pelvic inflammatory disease, or PID. The bacteria travel upward from the cervix into the uterus, fallopian tubes, and ovaries. This triggers a strong immune response that, while trying to fight the infection, creates widespread inflammation and tissue damage. Over time, scar tissue forms inside the fallopian tubes, partially or completely blocking them.
Blocked fallopian tubes prevent sperm from reaching an egg or stop a fertilized embryo from traveling to the uterus. This condition, called tubal factor infertility, is one of the leading causes of infertility worldwide. The damage is permanent. Even after the chlamydia itself is treated with antibiotics, the scarring remains. PID can also cause chronic pelvic pain that persists for months or years, and it significantly increases the risk of ectopic pregnancy, where a fertilized egg implants in the fallopian tube instead of the uterus.
What makes this especially frustrating is that PID can develop without noticeable symptoms. A woman may not know anything is wrong until she has difficulty getting pregnant years later.
Complications in Men
In men, untreated chlamydia most commonly causes epididymitis, an infection of the coiled tube at the back of the testicle that stores and carries sperm. Symptoms include a swollen or warm scrotum, testicle pain that develops gradually (usually on one side), an urgent need to urinate, penile discharge, and sometimes blood in the semen. If the infection spreads from the epididymis into the testicle itself, the condition becomes more serious.
Complications of epididymitis include abscess formation, fluid buildup around the testicle, and in rare cases, reduced fertility. While male infertility from chlamydia is less common than female infertility, it does happen, particularly with repeated or prolonged infections.
Risks During Pregnancy and for Newborns
Chlamydia during pregnancy carries real risks for both the mother and baby. A population-based study of over 4,000 pregnant women found that those with chlamydia had a four-fold increased risk of very early preterm delivery (before 32 weeks) and roughly 2.5 times the risk of delivery before 35 weeks, even after adjusting for factors like age, smoking, and ethnicity. The infection is also associated with premature rupture of membranes, low birthweight, and higher rates of perinatal mortality.
Babies born to mothers with active chlamydia face their own set of problems. Between 30% and 50% of these newborns develop conjunctivitis, a serious eye infection that appears 5 to 14 days after delivery. It causes swollen, red eyelids and pus-like discharge, and without treatment it can damage the eyes. Up to 20% of exposed newborns develop pneumonia, typically showing up between 1 and 3 months of age. About half of babies who get chlamydial pneumonia had conjunctivitis first.
Reactive Arthritis
Chlamydia can trigger problems far from the reproductive system. About 2% to 4% of people with a chlamydial urogenital infection develop reactive arthritis, a condition where the immune system’s response to the bacteria causes painful joint inflammation. The classic pattern involves three areas: joints, the urinary tract, and the eyes. In practice, most people don’t get all three at once.
Joint pain and swelling typically affect the knees, ankles, or feet. Eye inflammation can range from mild redness to more serious involvement. For most people, reactive arthritis resolves within months, but roughly 20% to 25% of patients progress to chronic complications affecting the joints, eyes, or even the heart.
Lymphogranuloma Venereum
Not all chlamydia strains behave the same way. Three specific subtypes (L1, L2, and L3) cause a more aggressive form of the infection called lymphogranuloma venereum, or LGV. This progresses through three stages. The first is a small, painless genital bump or sore that heals quickly and often goes unnoticed. Two to six weeks later, the second stage brings painful, swollen lymph nodes in the groin, usually on one side. The third stage, more common in women and men who have sex with men, involves severe inflammation of the rectum and colon.
LGV is less common than standard genital chlamydia, but the L2b subtype has been identified as playing a larger role than previously thought, circulating unrecognized in some populations for years.
Rectal and Throat Infections
Chlamydia doesn’t only infect the genitals. Rectal chlamydia occurs through receptive anal sex or through spread from a vaginal infection. When symptoms appear, they include rectal pain, discharge, and bleeding, but many rectal infections are completely silent. Chlamydia can also infect the throat through oral sex, though pharyngeal infections rarely cause noticeable symptoms and are often discovered only through targeted screening.
These extragenital infections matter because they’re easy to miss. Standard urine tests won’t detect them. If you’re at risk, site-specific testing (rectal or throat swabs) is the only way to know. The CDC recommends that men who have sex with men be screened at all sites of contact at least annually, and every 3 to 6 months if they’re on PrEP, living with HIV, or have multiple partners.