Trichomoniasis, commonly called trich, most often shows up as a yellow-green, frothy vaginal discharge with a strong, unpleasant odor. But the full picture varies depending on whether you’re looking at external symptoms, what a doctor sees during an exam, or what the parasite itself looks like under a microscope. About 70% of people with trich have no symptoms at all, which means the infection can look like nothing.
Discharge Color, Texture, and Smell
The most recognizable sign of trich in women is vaginal discharge that differs noticeably from normal. The discharge tends to be yellow-green or grayish, and it often has a thin, frothy, or bubbly texture. Many women describe a strong fishy or musty odor that can become more noticeable after sex. The volume of discharge is typically higher than usual.
That said, not every case produces textbook discharge. Some women notice only a slight increase in fluid or a subtle color change. Others have discharge that looks similar to bacterial vaginosis, a separate condition that also causes odor and a thin, grayish discharge. The two infections share enough overlapping features, including elevated vaginal pH and similar odor, that telling them apart by appearance alone is unreliable. One distinguishing clue: trich discharge is more likely to appear bubbly or foamy, while bacterial vaginosis discharge tends to be smooth and homogeneous.
Yeast infections, by contrast, produce a thick, white, cottage cheese-like discharge with little odor. If your discharge is thin, colored, and smells strongly, trich or bacterial vaginosis is more likely than yeast.
What It Looks Like on the Skin
Beyond discharge, trich causes visible inflammation of the external genitals. Women often notice redness, swelling, and soreness around the vulva and vaginal opening. The skin may appear irritated or feel raw, and some women report a change in skin color in the area. This inflammation can range from mild pinkness to pronounced redness and swelling, depending on how strongly your body reacts to the parasite.
Itching and burning are common alongside the visible changes, particularly during urination or sex. The infection targets the lower genital tract, including the vagina, vulva, cervix, and urethral opening, so irritation can show up at any of those sites.
What a Doctor Sees During an Exam
During a pelvic exam, a healthcare provider may spot signs that aren’t visible from the outside. The most distinctive is called a “strawberry cervix,” where the surface of the cervix is dotted with tiny red spots. These are small areas of bleeding (punctate hemorrhages) along with raised bumps on the cervical surface. The pattern looks remarkably like the surface of a strawberry.
This finding is considered a hallmark of trich when it appears, but it only shows up in a minority of cases. One study found the characteristic “moth-eaten” cervical appearance in about 13% of women with confirmed trichomoniasis. So while a strawberry cervix is a strong indicator, most women with trich won’t have one.
Symptoms in Men
Trich looks quite different in men, partly because it often causes no visible signs at all. When symptoms do appear, they typically involve the urethra. Men may notice a small amount of discharge from the tip of the penis, which can be cloudy, white, or slightly yellow. There may also be mild redness or irritation at the urethral opening.
Burning during urination or after ejaculation is the more common complaint, but these sensations don’t produce anything visible. Because men’s symptoms are so subtle or absent, many carry and transmit the infection without ever realizing it.
The Parasite Under a Microscope
If you’re curious about what the organism itself looks like, the parasite that causes trich is a single-celled organism called Trichomonas vaginalis. Under a microscope, it’s pear-shaped or oval, averaging about 10 micrometers long and 7 wide, making it slightly larger than a white blood cell. It has several whip-like tails (flagella) and a rippling membrane along one side that give it a distinctive quivering, jerky movement. That twitchy motion is often the first thing a lab technician notices when examining a sample.
When the parasite attaches to the cells lining the vagina, it flattens out and takes on a more irregular, amoeba-like shape, which can make it harder to identify. On Pap smears, it sometimes rounds up and looks similar to white blood cells, which is one reason Pap smears aren’t a reliable way to diagnose trich.
Why It Can Look Like Nothing
The majority of trich infections produce no visible symptoms. Among those who do develop symptoms, the onset can be delayed. Signs may appear within 5 to 28 days of exposure, or they may not appear for weeks or months. Some people carry the infection for long periods without any change in discharge, skin appearance, or comfort.
This is why trich is so commonly missed. If you’re relying on visible signs to tell you something is wrong, you’ll miss most cases. The traditional diagnostic method, examining a drop of vaginal fluid under a microscope (called a wet mount), only catches 44% to 68% of infections. Modern molecular tests that detect the parasite’s genetic material are far more accurate, with sensitivity above 95%. These are now the preferred method of diagnosis, and they can be run on a vaginal swab or urine sample.
How Trich Differs From Other Infections
Because several common vaginal infections share overlapping symptoms, here’s how to distinguish them visually:
- Trichomoniasis: Yellow-green or gray discharge, frothy or bubbly, strong odor, redness and swelling of the vulva, possible burning during urination.
- Bacterial vaginosis: Thin, grayish-white discharge, smooth (not frothy), fishy odor especially after sex, usually without significant redness or swelling.
- Yeast infection: Thick, white, clumpy discharge, little or no odor, intense itching, redness and swelling of the vulva.
These distinctions are helpful as general patterns, but they’re not foolproof. Research shows that the main characteristics of vaginal discharge, including amount, consistency, color, and odor, are only “poorly discriminative” between bacterial vaginosis and trichomoniasis. Mixed infections also occur. Testing is the only way to know for certain which infection you’re dealing with, and that matters because the treatments differ.