Pinworms look like tiny, thin pieces of white thread on the skin. Adult females, the ones you’re most likely to spot, measure 8 to 13 mm long (roughly the length of a staple) and are about half a millimeter wide. Males are much smaller, only 2 to 5 mm, and rarely visible outside the body. The worms are white or cream-colored, slightly curved, and may wiggle slowly when alive.
Where and When You’ll See Them
Pinworms are almost exclusively found on the skin directly around the anus. Female worms crawl out of the intestine while the infected person sleeps to lay eggs in the surrounding skin folds. This is why nighttime itching is the hallmark symptom of an infection.
If you’re trying to confirm a pinworm infection, the best window to look is 2 to 3 hours after the person falls asleep. Use a flashlight and gently check the skin around the anus. You may see one or more small white worms, sometimes moving slowly. During the day, they retreat back inside the intestine, so daytime checks are usually unreliable.
What Pinworm Eggs Look Like
You won’t be able to see pinworm eggs with the naked eye. They’re microscopic, and a single female can deposit thousands of them in the skin folds overnight. The eggs are what cause the intense itching, and they’re also what spread the infection, since scratching transfers them to fingers, bedding, and clothing.
To detect eggs, doctors use a simple tape test. You press a strip of clear adhesive tape firmly against the skin around the anus first thing in the morning, before bathing. The eggs stick to the tape, which is then placed on a glass slide and examined under a microscope. This test sometimes needs to be repeated on three separate mornings to catch the eggs, since females don’t always lay every night.
What Pinworms Don’t Look Like
Because people are often anxious when checking, it’s easy to mistake small bits of lint, toilet paper residue, or clothing fibers for worms. A few differences help you tell them apart. Pinworms have a consistent white, smooth appearance, slightly tapered at both ends, and living worms will show subtle movement. Thread or lint tends to be irregular in shape, may have color variation, and obviously won’t move. If you’re unsure, the tape test is the most reliable way to confirm.
Pinworms also don’t burrow into the skin or cause visible rashes on their own. However, persistent scratching from the itching can lead to redness, irritation, and in some cases a secondary bacterial skin infection if the scratched skin breaks open.
Symptoms That Accompany Visible Worms
The most common sign of a pinworm infection is anal itching that gets worse at night. Some people, especially children, also experience restless sleep, irritability, or difficulty staying asleep. In many cases, the infection causes no symptoms at all beyond mild itching, and some people only discover it after spotting a worm during a nighttime check.
If the skin around the anus looks red, raw, or shows signs of broken skin, that’s typically from repeated scratching rather than from the worms themselves. Keeping fingernails short and washing hands frequently helps prevent both reinfection and skin breakdown.
How Pinworm Infections Are Treated
Pinworm infections are treated with a single oral dose of an over-the-counter antiparasitic medication, available at most pharmacies without a prescription. The dose is based on body weight and is safe for adults and children over 2 years old. A second dose is typically taken two weeks later to catch any worms that hatched after the first treatment.
Because pinworm eggs spread so easily through a household, it’s common practice to treat everyone living in the home at the same time, even if only one person has symptoms. On the day of treatment, wash all bedding, towels, and pajamas in hot water. The eggs can survive on surfaces for two to three weeks, so thorough cleaning of bathrooms and bedrooms reduces the chance of reinfection.
Pinworm infections are extremely common, especially in school-age children, and they’re not a sign of poor hygiene. Most infections clear up quickly with treatment, though reinfection is common if eggs linger in the home environment.