Pinworms
A common, treatable intestinal worm infection that causes nighttime itching
Quick Facts
- Type: Intestinal parasite infection
- Cause: Enterobius vermicularis worms
- Main symptom: Nighttime anal itching
- Most affected: School-age children
Overview
Pinworms are small, thin, white worms, about the length of a staple, that infect the human intestine. The infection, called enterobiasis, is one of the most common worm infections, particularly in school-age children. Adult worms live in the lower bowel, and at night the females travel to the area around the anus to lay their eggs, which causes the characteristic itching.
Pinworm infection is usually harmless and rarely causes serious health problems. It spreads very easily, however, and often affects several members of a household. The good news is that it is straightforward to treat with medication and improved hygiene.
Because pinworm eggs are tiny and easily spread from hand to mouth and onto surfaces, the infection can pass quickly between people, especially in families and childcare settings. This is why treatment usually combines medication with simple hygiene steps to stop reinfection.
Symptoms
Many people with pinworms have mild or no symptoms. When symptoms occur, they typically include:
- Itching around the anus, especially at night when the female worms lay eggs
- Disturbed sleep and restlessness from the itching
- Irritability, particularly in children
- Itching or irritation of the vulva in girls if worms migrate there
- Occasionally, mild abdominal discomfort
Sometimes the tiny white worms can be seen around the anus or in the stool, particularly a few hours after the child falls asleep. Scratching can cause irritation or a secondary skin infection.
Causes
Pinworm infection is caused by the worm Enterobius vermicularis. People become infected by swallowing pinworm eggs, which then hatch in the intestine and grow into adult worms.
The cycle continues because the female worms lay sticky eggs around the anus, which cause itching. When a person scratches, eggs collect under the fingernails and are then transferred to the mouth, food, surfaces, toys, bedding, and clothing. Eggs can survive on surfaces for some time, allowing the infection to spread easily among family members and within schools and childcare settings.
Risk Factors
- Being a school-age child or caring for one
- Living in the same household as an infected person
- Attending or working in childcare centers and schools
- Frequent thumb-sucking or nail-biting
- Infrequent handwashing, especially before eating and after using the toilet
Diagnosis
Pinworms can often be diagnosed from the typical nighttime itching and by seeing the worms, but a simple test confirms it:
- Tape test: Pressing clear sticky tape against the skin around the anus first thing in the morning, before washing, to pick up eggs that can then be examined under a microscope.
- Visual inspection: Looking for the small white worms around the anus a few hours after the person is asleep.
Stool tests are usually not helpful because the eggs are deposited on the skin rather than passed in the stool.
Treatment
Pinworm infection is easily treated with medication, usually combined with steps to prevent reinfection.
- Anti-worm medication: Over-the-counter or prescription medicines such as pyrantel pamoate, mebendazole, or albendazole are very effective. A second dose is often given about two weeks later to kill any newly hatched worms.
- Treating the household: Because the infection spreads so easily, all household members are often treated at the same time.
- Hygiene measures: Washing hands well, keeping nails short, showering in the morning, and washing bedding and underwear in hot water help clear the infection and prevent its return.
Treatment is generally very effective, and most people recover quickly once medication and good hygiene are combined.
Prevention
- Wash hands thoroughly with soap and water before eating and after using the toilet or changing diapers
- Keep fingernails short and discourage nail-biting and thumb-sucking in children
- Shower in the morning to remove eggs laid overnight
- Wash underwear, pajamas, bedding, and towels in hot water regularly during treatment
- Avoid sharing towels and encourage handwashing at school and childcare
When to See a Doctor
See a doctor or pharmacist if you suspect pinworms, especially for very young children or if symptoms persist after treatment. Seek medical advice if scratching has led to a skin infection, if there is severe abdominal pain, or if a girl develops vaginal or urinary symptoms that may need separate evaluation.
Pinworms are not an emergency, but persistent or recurring infection should be reviewed so that all household members can be treated and reinfection prevented.
Frequently Asked Questions
How do you get pinworms?
You get pinworms by swallowing their eggs, often after touching contaminated surfaces, bedding, or food, or by transferring eggs from the anal area to the mouth via the hands. The eggs hatch in the intestine and grow into adult worms, continuing the cycle.
Why is the itching worse at night?
The female worms travel to the skin around the anus at night to lay their eggs, and this is what causes the itching. The disturbance is often most noticeable a few hours after a child falls asleep.
Should the whole family be treated?
Often yes. Pinworms spread very easily within a household, so doctors frequently recommend treating all household members at the same time and repeating the dose after about two weeks to prevent reinfection.
Are pinworms dangerous?
Pinworms are usually harmless and rarely cause serious problems. The main issues are itching, disturbed sleep, and easy spread. Persistent scratching can occasionally lead to a skin infection that needs treatment.
How can I stop pinworms from coming back?
Wash hands well before eating and after using the toilet, keep nails short, shower in the morning, and wash underwear, pajamas, and bedding in hot water during treatment. Treating everyone in the household at once also helps prevent reinfection.
References
- Centers for Disease Control and Prevention (CDC). Enterobiasis (Pinworm Infection).
- Mayo Clinic. Pinworm infection.
- MedlinePlus, U.S. National Library of Medicine. Pinworms.
- American Academy of Pediatrics. Pinworms.