Pinworms cause intense itching around the anus, most noticeably at night. The sensation is often described as a crawling or tickling feeling that gets worse when you’re lying still in bed. This happens because female pinworms physically migrate out of the intestine to lay eggs on the surrounding skin while you sleep.
Why the Itching Happens at Night
Female pinworms live in the large intestine during the day, but at night they travel to the skin around the anus to deposit eggs. These worms are small but not microscopic: females measure 8 to 13 millimeters long (roughly the size of a staple), while males are much smaller at about 2.5 millimeters. The physical movement of the worm across sensitive skin is what creates that distinctive crawling sensation.
The eggs themselves also contribute to the itch. When the female deposits them, she secretes a sticky substance that irritates the skin and triggers an urge to scratch. Scratching picks up eggs on your fingers and under your fingernails, which is how the infection spreads, both to other people and back to yourself when you touch your mouth.
The Full Range of Symptoms
The hallmark symptom is perianal itching that worsens at night, but pinworms can cause a wider set of problems, especially in children. These include trouble falling or staying asleep, restlessness, irritability, teeth grinding, and occasional stomach pain or nausea. Many of these secondary symptoms stem from disrupted sleep rather than the worms themselves. A child who seems unusually cranky, is grinding their teeth at night, or has started bedwetting may be dealing with a pinworm infection even if they haven’t complained about itching.
In girls and women, pinworms can migrate from the anal area toward the vagina, causing vaginal itching and irritation. This is sometimes the most noticeable symptom and can be mistaken for a yeast infection or other condition.
Some people with pinworms feel almost nothing. Light infections can go completely unnoticed, with no itching or sleep disruption at all. The severity of symptoms generally tracks with how many worms are present.
How to Confirm It’s Pinworms
If you’re experiencing nighttime anal itching, the simplest way to check is the tape test. First thing in the morning, before showering, using the bathroom, or getting dressed, press the sticky side of a piece of clear tape against the skin near the anus. Any eggs present will stick to the tape. Seal it in a plastic bag and bring it to your doctor’s office, where the tape can be examined under a microscope. You’ll want to repeat this three mornings in a row, since the worms don’t necessarily lay eggs every single night.
You can also sometimes spot the worms directly. Check the skin around the anus two to three hours after bedtime using a flashlight. The female worms are thin, white, and thread-like. They’re small but visible to the naked eye.
How Pinworms Spread
Pinworm eggs are remarkably durable. They can survive two to three weeks on contaminated surfaces like bedding, towels, clothing, and toys. When someone scratches the itchy area, eggs get on their hands and transfer to everything they touch: doorknobs, countertops, shared food. Other people swallow the eggs unknowingly, and the cycle starts again. This is why pinworm infections are so common in households with young children and in settings like daycares and schools.
The eggs are also light enough to become airborne when you shake out bedding or clothing, which means you can inhale and swallow them without any direct contact with an infected person.
Treatment and Getting Rid of Them
Pinworm infections are treated with two doses of antiparasitic medication, spaced two weeks apart. The first dose kills the adult worms, but it can’t destroy eggs that are already laid. The second dose, taken exactly two weeks later, catches any newly hatched worms before they can mature and start laying eggs of their own. Skipping the second dose is one of the most common reasons the infection comes back.
Both over-the-counter and prescription options are available. Your doctor or pharmacist can help you choose the right one based on age and weight. In most cases, everyone in the household should be treated at the same time, even family members without symptoms, since the infection spreads so easily within a home.
Alongside medication, thorough cleaning makes a real difference. Wash all bedding, towels, and pajamas in hot water on the morning treatment starts. Shower in the morning rather than at night to remove eggs deposited overnight. Keep fingernails trimmed short, and encourage frequent handwashing, especially before meals. These steps help break the reinfection cycle that keeps pinworms coming back even after treatment.